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Ozo s texture pack 1-3 2-4 betting system sports betting simplified

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In general, on a unit-area basis, the optimal fertilizer rate is greater for oranges C. These rates are somewhat greater than the recommended N rates; i. With recent trend towards high density planting and considerably greater fruit yields ha-1, the N required kg-1 fruit could be somewhat lower than those reported previously. With intensive production practices, fruit yields of up to 70 Mg ha-1 are not uncommon.

On the basis of the above N requirement guidelines, the N rate required to support 70 Mg ha1 would represent around and kg N ha-1 yr1 respectively, for oranges and grapefruit. However, current fertilization practices are well below these rates. This increased efficiency of N use in the recent years can be attributed to improved management and scheduling of irrigation and fertilization Alva and Paramasivam, Fruit Quality Fruit quality affects economic returns, especially for the fresh fruit market, and therefore is an important component of citrus production.

The amount of N required for maximum or optimal yield of citrus fruit. In general, increasing N rate tends to: l increase juice volume, total soluble solids TSS , acid content, and juice color; 2 increase number of green fruit at harvest and incidence of creasing and scab; and 3 decrease fruit size, weight, and peel thickness.

Increasing rate of P decreases acid content, increases Brix:acid ratio and number of green fruit, reduces peel thickness, and increases expression of wind scar. Increasing the rate ofK decreases injuice content, solids, Brix:acid ratio, and juice color, while increasing fruit-acid content, fruit size, weight, peel thickness, and green fruit number Boman, ; Calvert, , ; Calvert and Reitz, ; Embleton et al.

There are strong interactions among N, P, and K with respect to their effects on fruit quality. For instance, the effect of increasing N application on fruit size may be countered by simultaneous increase in K rate. An increase in N rate is accompanied by a proportional increase in P and K.

The effect of fertilization on fruit quality is a comprehensive result of N, P, and K interactions. Therefore, it may be more meaningful to examine the effects of fertilizer rate rather than the amount of individual nutrients on fruit quality. A summary of effects of fertilizer rates on fruit qualities of White Marsh grapefruit is shown in Table 2.

When using a mixed fertilizer blend containing N:P:K ratio of Peel thickness, which is related to fruit size, declines at higher fertilizer rates Table 2. Therefore, if a large grapefruit is desired, an N rate kg ha1 yr1 with. A systematic report about effect of fertilizer rate on orange quality is not currently available.

However, similar results are expected regarding the effects of fertilizer rate on fruit size and peel thickness of oranges. Increase in N rates from 0 to kg ha1 yr1 increased TSS and fruit-acid content of grapefruit Table 2. The fertilization rate effect on fruit Brix content was more complicated. Brix content was not affected by N rate in the range of O to kg ha1 yr1 but increased bv increasing N rates from to kg ha I yr1 Therefore, the Brix:acid ratio generally decreased with N fertilizer rates Table 2.

The philosophy of BMPs is to maximize nutrient uptake by minimizing various losses. This will maximize economic returns and minimize residual nutrients in soil susceptible to leaching loss. Citrus trees with low nutrient status usually have higher nutrient uptake efficiency than trees with high Table 2. Effects of N fertilization on fruit quality of White Marsh grape fruit.

J:P:K 1 For mat. Nutrient Removal by Harvested Fruit The percentage of nutrients removed by harvested fruit compared with the total amount applied can he a measure of nutrient uptake efficiency for mature citrus trees. The amounts of N and K removed bY harn.

Critical concentrations of N, P, and Kin 6-mo-old spring flush leaves needed for optimal yield of citrus. Relative fruit yield of the grapefruit was, however, q naclratically related to leaf N concentration Fig. For P and K, the critical leaf concentrations were 1. These standards are in close agreement with those proposed by Reitz and Hunziker Fertigation, Controlled Release Fertilizer Source vs. Water Soluble Granular Form Water-soluble granular fertilizer has been the major form of fertilizer used by the Florida citrus industry.

These results suggest nutrient uptake efficiency may be greater with fertigation as compared with the application of water-soluble granular fertilizers. Controlled-release fertilizers contain one or more plant nutrients in a form that either delays nutrient availability or extends its availability Mortvedt and Sine, Controlled-release fertilizers applied in part or throughout a fertilization program have been observed to significantly reduce N leaching in citrus cropping systems on sandy soils in Florida Alva and Paramasivam, ; Wang and Alva, Greater tree growth and fruit yield have been reported using controlled release fertilizers as compared with water soluble granular fertilizer Boman, ; Alva and Paramasi vam, ; Obreza et al.

A recent study by Obreza et al. However, because of its greater cost, the economic feasibility of using controlled-release fertilizers for citrus production needs to be further evaluated. Table 5. Increase in fruit yield by fertigation as compared to that with broadcast of watersoluble grannlar.

In another study in west central FloricLt, occasionally NO,-N concentrations in groundwater were observed to exceed 10 mg L', even at 3-m depth below land surface on flatwoods soil McNeal et al. The potential for nitrate leaching is greater in ridge areas of deep sand in central Florida. Solution P04 -p concentrations at the cm depth average 0. Soil water above this depth mav seep into water furrows through lateral rnovcment and be discharged into surface drainage water He et al.

A column leaching study conducted by He et al. The argillic horizon had much less effect on tlic nTtical transport of NO 1-N along the soil profile He et al. Cnder field conditions, the denitrification process mav be an important mechanism that keeps NO, concentrations at rela tively low levels in the flatwoods soils, as denitrification generally increases with the availability of NC , and or-Table 6. The potential maximum NH.

JO, g kg Ammonia volatilization was minimal at soil pH of 3. The potential maximum T',,;I L, volatilization increased by 2-and 3-fold, with an increase in temperat11re from 5 to 25C. The greath' enhanced NII, volatilization at 45C:, as compared with that at 25C, was related to the inhibition of nitrification at the high temperature, which incrc. Under field conditions in a citrus grove I 00 to g kg-1 N loss by NH, volatilization measured using sponge-tracking techniques was also observed ParamasiYam et aL, Application of cellulose increased the microbial biomass, thus enhancing immobilization of applied N and decreasing volatilization loss.

The effect of CZ appears to be related to increased retention or NH,' in the cationexchange sites. The strong positive interaction between cellulose or CZ amendment and microbial biomass resulted from improved water and nutrient retention in the soil and availability to microorganisms.

Best management p1actices for irrigation and frnilization of flol'ida citrus in Flatwoods soils. Project Completion Rep. Contract No: 93W , Fla. Soil Sci. Plant Anal. Alva, A. K, and S. J l:i Impact of nitrogen management practices on nutritional status and yield of Valencia or:1nge and ground waler nitrate'.

J Environ. Boman, B. J A comparison of controlled-release ru convent ion al fertilizer on mature 'Marsh grapefruit. State Hort. Homan, B. Effects offrrtili1ation and potash source on grapefruit size and yield. Fertilization, Israel Inst. J G. Fertigalion ,ersus conn,ntional fenilization o! Flalwoods grapefruit. Calvert, D. Effects of rate and frequencv of fertilizer applications on growth. Response of "Temple" oranges to varying rates of nitrogen.

S1ate Hort. Nitrate, phosphate, and potassium movement into drainage lines under three soil management svstems. An evaluation of grapefruit leaf nutrient concentrations vs. Aha, Y C. Li and D. In Agronomy abstracts. ASA, Madison. Soil :me! Crop Sci. Florida Proc. J Reitz. A fertilizer study with Valencia oranges in Lhe Indian River area. Ell'ccts ol r. Li, and D. Llfects of nitrogen krtilization ol"grapefruit trees on soil acidification and nutrient availability in a Riviera fine sand.

Plant Soil I J Hutchinson, C. Science iEi. Koo, R. The influence of N, K, and irrigation on tree size and fruit prnduction ol 'Valencia orange. Results of citnis fertigation studies. Tucker, D. Recommended fenili1 " Ruprecht, R. Citrus fertilizer expnirnents. State 1 lort. The rate and timing of nitrogen for grapefruit on Lakeland fine sand.

Hochmuth ABSTRACT Vegetables are produced on nearly acres ha in Florida and fertilization is important for profitable production of high-quality vegetables in this state. Optimum management of nutrients for vegetable production is important for several reasons. Secondly, nutrients, such as N or K can be mobile in the sandy soils of Florida and this is a particular problem under heavy rainfall or excessive irrigation.

Finally, nutrient management is important because nutrients lost to the environment can negatively impact the quality of ground or surface waters. Vegetable growers have several technologies within their reach to maximize nutrient management, including calibrated soil testing, polyethylene mulch, fertigation, controlled-release fertilizers, and plant tissue testing, among others.

In addition to these technologies pertaining directly to nutrient management, growers have new information on optimum irrigation management at the farm level. Water management on the farm is critical to successful nutrient management. Commercial vegetable producers in Florida face many challenges for profitable crop production.

There are severe economic challenges, including competition from other countries as well as intrastate competition. Costs of production co11tinue to rise. There arc cstant pressures from new insect and disease pests. Each of these new pests requires new crop and pest management strategies to minimize the negative impacts of the new pest.

Farmers face continual risks from nature, including freezes, floods, and droughts, all of which cause crop losses and add to the costs of production. These laws add more costs to the farm for compliance. Fertilizer management is important for successful yegetable crop production, but scyeral issues impact how fertilizer is managed on the farm.

Concern over nutrient contamination of the environment has led to interest, on the part of governmental regulators, in the implementation of best management practices BMP on the farm. A nutrient management BMP can be thought of as an integrated system for supplying nutrients for economical crop production and which maintains environmental nutrient standards. The pollution issue is particularly acute in southern Florida with G. Hochmuth, North Florida Res.

Center and Horticultural Sciences Dep.. Florida Agric. Journal Series No. Moreover, recently it was documented that insect populations and damage can be enhanced with excessive N Funderburk et al.. One of the most important factors in optimum nutrient management is knowledge about crop nutrient requirements for the yegetable being produced. Often, fertilizer alllounts are set based expected yields.

As fertilization rates increase, yield will increase to a certain point, after which more fertilizer onlv leads to fertili7cr being left behind in or below the root zone. These nutrient requirements art' the result of significant research with vegetables, in some cases, for more than 50 yr. Recently, the vegetable fertilization literature was summarized for 11 vegetables Hochmuth and Cordasco.

This sun ev of' 1. Calibrated soil testing is used to determine the part of the crop nutrient requirement that can be supplied hy the unfertilized soil. Many commercial and public labs are available for soil testing, but not all can reliably interpret test results for soils in Florida. Growers need to choose a competent lab that uses soil-testing procedures calibrated for Florida.

There are several philosophical approaches to making fertilizer recommendations, causing confusion among soil testing lab clients Olson ct al. Onlv the percent suHiciency approach to making fertilizer recommendations should be used in Florida. This approach makes a fe:Ttilizer recommendation taking into account the amount of crop available nutrients already in the soil. Fertilizer might not be recommended when the soil already contains enough nutrients for optimum crop production.

The calibration is especially supported for I' but less so for K. The mobility ofK is tht' main reason for the poorer calibration, compared Lo P, Soil testing for N is not calibrated in Florida because N is very mobile in the sandy Florida soils, and N fertilizer needs are difficult to predict based on a soil test, Once the fertilizer amounts have been determined, nutrient. For most Florida vegetables, a combination of preplant and postplant applications offertilizer are needed.

The reason for this is that fertilizer is subject to leaching losses, especially the mobile nutrients N and K. Most research shows that P should be applied to the soil in the bed area before planting. Tomatoes Lycopnsiron esculentum! The preplant-applied N and K should be incorporated in the bed area. For 1nany vegeta bles, polyethylene rnlllch protects mobile nutrients from leaching and could be considered a component of a nutrient management BMP Hochmuth, Controlled-release fertilizers have been shown to have positive effects on vegetable yields in Florida Lo cascio ct al.

Selection of nlltrient sources should be made based on nutrient content and cost factors. Research has shown lhat the source of soluble Nor K rarely affects vegetable crop performance Locascio et al. Cook and Sanders. Nitrogen and K fertilizer should be injected according to a schedule based on crop growth and nutrient demand Hartz and Hochmuth, ; Hochmuth, a; b.

For unrnulched crops, the remaining N and K fertilizers art' applied to the soil in bands near the crop in two or three applications during the crop growing seasons. For crops grmring on mulch and drip irriga tion, the N and K can be injected through the drip system in amounts according to crop growth. Schedules for N aml K injection into drip irrigation systems have been published for vegetables in Florida Hochmuth, a; Hochmuth and Smajstrla, Research result5 have shown that rarely will vegetables respond positively to more than 3 kg ha1d-1 Hochmuth, For mulched crops without drip irrigation requiring applications of nutrients during the season, the liquid fertilizer injection wheel can be employed Csizinszky et al.

The most important factor in optimum fertilizer management in Florida is water management. Excessive irrigation or he,ny rainfall can leach N and K from the soil, leading, in the case ofN, to negative environmental impacts. Irrigation should be scheduled to maintain soil moisture potential near -8 to cb kI'a Clark et al.

Amounts of irrigation water should be determined based on pan evaporation measurements Clark, ; Smajstrla and Locascio, El The goal is to employ an irrigation program that results in maintaining the water and nutrients in the root zone. Nutrients lost from the root zone are suhject to movement into the groundwater. Plant tissue testing can be used to fine-tune fertilization programs or to diagnose suspected nutritional problems Hochmuth ct al. There are two basic systems to use Cor plant tissue testing, standard laboratory analyses based on dried whole-leaves, and fresh petiole sap testing Ilochmuth et al.

Petiole sap analyses are especially useful for vegetahles growing on mulch and drip irrigation Hochmuth, ; Rhoads, ; Rhoads et al. Based on petiole sap analvses, small adjustments can be made in the injection schedule. Research conducted in Gainesville and Quincy, FL showed that there is an optimum time in the growing season for adjustments to the :injection of N for tomato Locascio et al.

Vegetable production in Florida requires sig11ificant amounts of inputs for profitable production of high-quality vegetables. Fertilizer is one ol these required inputs. Proper management of the nutrients used in vegetable culture is needed to ensure that the nutrients benefit profitable crop production and do not become an environmental contamination risk.

Fertilization is an important expense on the farm and its proper management is important to the future success of vegetable production in Florida. Hochmuth, C. K Chandler,J. Cornell, and. Potassium krtigation rrriuirerrn'nts of drip irrigated strawberrv. Albregts, E. Effect of fertilizer rate on number of malformed strawberry fruit. Clark, G. Andersen, and S. UV-reflective mulch and nitrogen fertility effects on western flower thrips and tomato spotted wilt ,irus in tomato.

Hartz, T. Fertility management of dripirrigated vegetables. HmlTechnology J a. Fertilizer ,magenH'lll for drip-irrigated, cgctablcs in Florida. I IortT,xhnology '. Hochmuth, G. Concepts and practices for improving nitrogen management for vegetables. Hon Technology 2: Nitrogen management practices for vegetable produnion in Florida.

Scnice Circ. Brecht, and M. Nitrogen fertilization to maximize carrot vield and quality on a sandy soil. Service Pub!. HS, http:! J Fertilizer lssues ' Smajstrla, A. Irrigation scheduling of dripirrigate lected ,egetables in Florida, EI There arc many attributes for effective media, including the ability to retain moisture and nutrients, ability lo provide good aeration and drainage, availability at an acceptable price, and chemical and physical attributes conducive for plant growth.

In recent years, there has been a trend in which more traditional organic components, such as peat or wood products, have been partly supplanted by an increasing array of waste-product compost products. This paper reviews some important issues in the utilization of urban waste compost products, such as plant response to different percentages of compost in the growing media as well as compost maturity.

Ornamental crop production is one of the m,uor types of horticultural production in Florida. Since in the 19th '. In recent years, the rate of increase has accelerated. There are certain unique attributes to or11ame11tal crop production in addition to its high and rapidly increasing economic value.

The vast majority of ornamental crops are now grown in containers and when the plant is sold, the rooting medium is sold with it. This ne cessitates the regular acquisition of new growing meclium supplies each time a new crop production cyde is begun. Some nurseries mix their own media while others purchase pre-rnixed media. While there is no perfect growing medium for all ornamental crops under all growing conditions, most growers want a grow i 11 g substrate that is consistent, reprodllcible, readily available, easy to work with, cost effective, and with the appropriate physical and chemical properties Poole et al.

U nifrmnity aud consistencv of physical and K.. Ionic11lt11re lkp. Lent er, ,l:! FL 3'l'. Florida Ag-ric. To achieve these criteria, growers and substrate producers combine different types and amounts of organic and inorganic components. Peat is most traditionally nsed as the organic component in horticultural substrates.

Peat is a naturally occurring material formed chiefly from the partial d avoid this problem, manv wood products are composted before they are used as components in growing substrates. Composting is the controlled decomposition of organic matter to a point where the product can be safelv and beneficially used Rodak et al.

Other organic materials besides wood products also can and are Table 1. General recommendations for physical and chemical properties of container growing media for bedding plants, foliage plants, and woody ornamentals Fonteno, ; Warncke and Krauskopf, ; Poole et al. Increasing urbanization throughout the 20th century has created concentrated populations producing large amounts of urban waste products.

Plant responses to increasing quantities of compost in the growing media are variable. Some compost products can produce larger plants than control substrates, but to be cost effective for ornamental plant production, compost products only have to be equally effective as the control medium if it is available for a comparable price. In a study with three subtropical ornamental species, Fitzpatrick did not observe any significant differences in growth of jasmine Jasmine volubile Jacq.

However, growth of ligustrum J,igustrum japonicum Thunb. Because of the highly diverse nature of urban waste, the use of urban waste compost as a component in the growing media for ornamental plants can be challenging. For example, Fitzpatrick reported that dwarf schefflera Schefflera arboricola Haya ta and spathiphyllum Spathiphyllum Schott.

However, plants grown in the biosolids compost that had been made from chemically-treated biosolid produced smaller plants than plants grown in the compost made from untreated biosolids. The chemically-treated biosolid compost had substantially higher soluble salt concentrations than the untreated biosolids compost. Both begonia Begonia x semperjlorens-cultorum Hort. Compost maturity is one of the most important factors to understand before using compost products in the growing substrate.

Reasons for the disparity between the compost types included higher soluble salt levels in the municipal solid waste compost and that the municipal solid waste compost was less mature with a C:N of 29 compared to a C:N of 17 for the biosolids compost.

Example of bioassay using radish seeds. The flat filled with the control medium is on the left while the flat filled with the compost in question 4-wk-old municipal solid waste compost is on the right. It is difficult to define one set of recommendations that apply for all compost use in container production.

The appropriate amount of compost to use in container media will vary with the type of plant being grown as well as with the compost product. Furthermore, it is difficult to recommend one compost product over another. Growers should look for compost products that will meet the physical and chemical parameters for the crop that they are growing.

In general, compost products suitable for container use should be to inch mm particle size and should have a pH of 5. The nursery industry's impact on Florida's economy. Ornamental Outlook 8 2. Dickey, R.

Conover, and J. Container growing of woody ornamental nursery plants in Fl01 ida. Fitzpatrick, G. Compost utilization in ornamental and nurs ery crop production systems. In Stofella and Kahn ed. Compost utilization in horticultural crop systems. Sludge processing effects on compost quality. BioCycle 27 9 Evaluation of potting mixes derived from urban waste products. Fonteno, W. Reed ed. Water, media, and nutrition of greenhouse crops. Ball Pub. Batavia, IL. Jimenez, E. Evaluation of city refuse compost maturity: a review.

Wastes Klock-Moore, K. Bedding plant growth in greenhouse waste and biosolid compost. HortTechnology 9 2 Klock, K. Growth of Impatiens 'Accent Red' in three compost products. Compost Sci. Leege, P. Thompson ed.

Test methods for the examination of composting and compost, 1st ed. The C. Composting Council, Bethesda, MD. National Bark and Soil Producers Association. Uniform nomenclature for quality soil products. Available at www. Nelson, P. Root substrate. In Greenhouse operation and management 5th ed. Obeng, L. The cocomposting of domestic solid and human wastes. World Bank Tech. Poole, R. Conover, and. Soils and potting mixtures. Joiner ed. Foliage plant production. Olds, M. Goldman, M. Franz, and].

The complete book of composting. Rodale Books, Emmaus, PA. Rynk, R. Willson, M. Singley, T. Kolega, F. Gouin, L. Kay, D. Murphv, H. Hoitink, and W. On-farm composting handbook. Ithaca, NY Warncke, D. Greenhouse growth me dia: Testing and nutrition guidelines. Michigan State Cniv. Facts Ext. East Lansing. Whitcomb, C.

Growth media. In Plant production in containers. Lacebark Pub. Stoffella, and H. Soil organic amendments are usually in the form of animal manures, green manures cover crops , and composts. Composts, derived from various organic wastes, have become increasingly popular soil organic amendments. Research has demonstrated that compost can serve as a soil amendment to increase organic matter, improve microbial activities in soil, provide nutrients, and ultimately improve plant growth and yield.

However, composts are produced from various organic wastes and consequently, environmental concerns are always an issue in compost utilization. The potential often exists for heavy metals to accumulate in the soil and sometimes in the edible parts of vegetable plants. Excessive nutrients or metals released from composts may be leached out of the root zone and into groundwater by irrigation or by rainfall.

Vegetable crops are grown mostlv on sandv or gravelly soils with a small but significant J;ortion on ,His tosols organic soils. These soils, excluding Histosols. Using organic materials as soil amendments on Florida soils usuallv improves soil fertility and generally, but not always increases crop vields. Indeed, animal manures supplv significant quantities of' essential pla11t nutrients and increase soil organic matter Hochmuth t't al. Cover crops are used to improve soil physical properties, increase soil organic carbon, conserve soil water, reduce surface runoff, and recycle nutrients during the heavy summer rains Hubbell and Sartain, l S 80; Reeves, ; Mansoer et al.

Sunn hemp Cmtrilaria juncea L. Li and H. Bryan, Tropical Res. Center, liniv. Stoflella, Indian River Res. Center, Univ. Pierce, FL , Contribution published in Soil Crnp Sci. A series or co, er crop projects an--cnrrently in progrt'ss in south Florida. Composts have been increasing in popularity as soil orga1:ic amendments. Compost application to commercial vegetable crops is relatively new in Florida. In this paper we briefly review the horticultural and c11,irnnmental effects of compost utiliz,1-tion in commercial vegetable crop production systems in Florida.

Mineralization of a compost depends on the compost's composition, ma turity, and the soil conditions moisture, temperature, etc. Elemental composition of three typical composts used for vegetable production in south Florida Zhao et al.

Mg, and P increased, whereas extractable K was not affected. Similar Ii ndings were also reponed b, Clark et al. Hoffmann reported that repeated applications of MSW compost over a long-term increased soil organic C from 20 to 62 g kg-'. The amendment of soil with compost increases humus formation.

Humic acid is a major extractable component of soil humic substances; FA is usually a minor component of soil: and soil humin is a major nonextractable component Stott and Martin, Bovd and Sommers reported that soils amended with sewage sludge had 5 and?

Glucosidases or glycoside hydrolases are en' zymes that catalvze the hydrolysis of various glycosides. Indeed, the hydrolysis products of 0-glucosidase arc helie,ed to be important energy sources for microorganisms in soils Tate, 19 5. Zhao et al. Dehydrogenase, urease, pyrophosphatase, and 0-glucosidase activities were positively affected by addition of these three composts to soils.

The cocompost treatment signihcantlv increased all enzvnw activities except pyropl10sphatase. En zyme activities, except that of pvrophosphatase, were the lowest in plots treated with inorganic fertilizer. The levels of dchydrogenase, urease, and pvrophosphatase activities resulting from addition of organic residues began to decline about 30 d after application of soil amendments. Bv contrast, 0-glucosidase in co-compost amended soil remained 5 Lo 7 times higher throughout the entire d experimental period than in other treatments in which organic matt.

No similarly effective soil fumigant is commercially available. Hoitink et al. The high level of microbial activity in the biomass is attributed Lo the general soil microflura. It is believed to pren:nt the germination of the spores of pathogens and thereby avert infection of the host.

Such disease suppression properties are dependent on compost composition and maturity, organisms to be suppressed, and environmental conditions. Composts have been evaluated for their capacities to suppress nematodes and plant pathogens in Florida. Composts have had inconsistent effects on nematodes and plant pathogens affecting field or greenho11se grown vegetable crops Table 2.

Bryan et al. However, using similar composts, Mannion et al. Thcv reported no ef fects of compost amendments on plant-parasitic nematode populations during a 2 yr experiment. Ritzinger et al. Ozores-Hampton ct al. In most experiments. Responses of vegetable growth are significantly affected by compost composition, maturitv, and soil conditions. For example, effects of composts on tomato yield are presented in Table 3. Obrcza ancl Reeder also suggested that the lower yields of to mato from compost amended plots in their experiment had been caused by incorporating immatun compost.

Therefore, responses of crop to compost amendments is largely depended on compost quality. Clearly, reliable methods to determine compost maturity and stability and pathogen suppressivity should be developt'd. Of parlicular concern is the possi-Table 2. Effects of compost amendment on the incidence of nematodes and bacterial wilts of vegetables grown in Florida. Yield responses of tomato to compost amendments from experiments conducted in Florida. Excess nutrients or metals released from composts may be leached from the root zone by irrigation or rainfall Li et al.

During to , Zinati ct al. One of three composts used in the experiment significantly increased concentrations of Ni and Pb in amended soils. They reported no significant changes in concentrat. Nutrient leaching rates in Florida from sugarcane filtercake, biosolids, and three mixtures of MSW, and biosolids applied to the surface or a Florida fine sa11dy soil have been evaluated Li et al. After leaching with water equivak11t to '.

The concentrations of N However, the U. Clearly, leaching of nutrients in relation to the drinking water standard must be considered in selecting compost application rates and frequencies, particularly on soils nilnerable to nutrient leaching. High variability in the quality of operations between and within compost production facilities leads to unpredictable compost quality. Often immature composts display plant phytotoxicity. Composts derived from organic wastes are Lhe most available soil organic amendment, and technology has been improving compost quality and quantity signifi cantly.

Sewage sludge compost's cumulative effects crnp growth and soil prnperties. Utilization 1 :'. Bmd, S. Hrnnic and f'ulvic acid fr"ctiom from sewage sludge. Humic substances in soil and crop scicnns. Madison, WI. Brown, R. Stone, and V. Myers and. Ecosystems of Florida. Sanford, and.

State 1-lml. Bryan, H. Effects ohoil fumigation. I I 0:'.! Effect of composted organic amendments on the incidence of bacterial wilt to tomato. Clark, C. Stanley, and D. Municipal solid waste compost in irrigated YCgctable production. Csizinszky, A. Respo11st of tomatoes to microirrigation rc1t,s, compost placement and rates and N and K sources. Dick, R. Influence of longterm residue management on soil enzyme activity in ralation to soil chemical properties of a wheat-fallow system.

Epstein, E. The science of composting. Tcchnomic Pub. Effecl of the application ot 1own rd Waslcs Goldstein, Y The state of garbage in America. Hanlon, E. Sch:dfrr, M. Ammonium hicarbonatc-OTPA ex1rac1ion of cleents from waste-amended calcareous soil.

He, X. Chemical properties of 1mrnicip,tl solid waste composts. He, Z. Yan, Y. Li, D. Calvert, P. Stoffella, and D. Hochmuth, R. Hochmuth, and M. Responses of cabbage yields, head quality, and leaf nutrient status, and of second-crop sq,rash, 10 poultry inure fenili1atio Hoffmann, G.

Recycling of municipal waste compost in vineyard soils. Studies about humus. Nmak ed. Abstracts , Prague, Hoitink, H. Stone, and D. Y Han. Suppression ul plant diseases lw composts. Hoiti11k, II. J Boehm. Status of compostedamended potting mixes natnrallv suppressive to soilhorne cliscases of llmicultuntl crops. Plant Dis. Legumes-a possible alternatiw to fertili,er nitrogen.

Hmnic substances formed drning the composting oforganiL m;uter. Kononoya, M. Soil org,mic matter. Pergamon Press, Elmsford, NY. Li, Y. What are miuerali,atiou rates ol composts in south Florida0 Vegetarian '. Stoffella, A. Aha, D. Calvert, and D. Leaching nt nitrate. J Compost Sci. Summer cover crops for tomato production in south Florida. Toma Lo lllsl. Schaller, M. Ozores-Hamplon, H. Brvan, and R. Nematode population dynamics in municipal solid waste amended soil during tom:ito and squash cultivation.

Suitability of su11n hemp as an alternative late-summer legume cover crop. Prnd11ction and persistence of soil cn,vmes with repeated ddclition ol organic residues. Shiralipom, and W. Compost application improve. B1Yan, and R.

Suppressing diseas iol Fert. Soils I '. Piu:rn10nti, F. Stringari, F. I kavy met;tls in apple orchards :dler the application of two composts. Reeves, D. C:overcroris and rotations. L llatfwld and B. Stewart ed. Stephens, j. Org:mic vegetable gardening. Stevenson, F. Humus chemistn: Genesis, composition, reactions. Stoffella, P. Organic wastt' compost utilization in vcgetahh-crop production.

Li, N. Roe, M. Ozores-Hampton, and D. Managing soil l'enilitv for int,"11sive vegetable production s1stems in Asia. Asian Veg. Center, Tainan, Taiwan. Svnthesis and degradation of natural and srnthetic hrnnic materi:tl in soils.

The advent of synthetic chemical fertilizers decreased organic fertilizer use such that it makes up only about 0. However, interest in applying organic amendments to citrus is rising because of increased supplies and decreased costs of non-hazardous organic wastes.

Citrus growers apply these materials for perceived or real improvements in soil physical, chemical, and biological properties, but the main benefit appears to he increased nutrient availability. The use of organic materials as an N source is being considered as a best management practice BMP for N management because organic N is released to the plant more gradually than water-soluble, inorganic fertilizer N.

Current organic amendments applied to citrus groves biosolids, poultry waste, and composts differ substantially from those applied in the past. Poultry waste is the most expensive, followed by compost and biosolids. Fourth Step Elicitation Estimates of mortality for a single species population, incorporating interspecific interaction and possible changes in trophic relationships occurring in three "representative" natural habitats.

I Metal Toxicity 69 Cu: Points are taken from the literature. Because a number of game fish would occupy similar positions within this framework, for example, brook trout and rain- bow trout, the actual number of elicitations would have been greater than three. Inquiry into non-game species was considered appropriate in order to better represent possible interspecific effects and food chain disruptions.

It was decided that the final determination of the fish species to be analyzed should be a product of the interview process between the investigators and the partici- pating scientist. Because fisheries scientists or ecologists are generally more familiar with certain fish species, it was assumed that results of the elicitation would be more reliable if participating scientists were able to specify those particular fish species for which they had the greatest confidence in their predictions.

As a consequence of this indeterminancy, the data obtained from the literature review was organized in parallel to the logic of the elicitation procedure whenever it was available see Figure Every reproductive stage of the fish species under consideration was evaluated in terms of percent survival relative to a set of water quality parameters.

The literature review revealed that certain metals are present in increased concentra- tions in acidic waters, namely zinc, manganese, and aluminum Schofield, Pre- sumably these elevated concentrations are a result of the increased solubility of these metals at lower pH values. Of these metals, only aluminum has been found to be toxic to fish at concentrations currently measured in acidified waters Baker ; Baker and Schofield ; Muniz and Leivestad, On the other hand, calcium has been shown to decrease the membrane permeability of fish undergoing acid stress, and consequently decrease the rate of sodium loss.

A number of investigators have observed correlations between decreased calcium content and fish mortality as well as correlation between increased calcium concentration and fish survival Spry, As a result, it was felt necessary to specify the concentrations of aluminum and calcium in the water for each pH level.

The relationships between aluminum, calcium and pH were taken from regres- sions computed by Schofield of Cornell University. A single species population consisting of all reproductive life stages was, by hypothesis, contained within a single flow through vessel. Assuming values for the elapsed maturation time of each reproductive stage then enabled esti- mates of class survivorship'at different pH levels. This "process was to be iterated through a complete reproductive cycle for each fish population.

The time allotted for maturation of each reproductive stage is shown in Table The second step was designed to capture the effects of declining pH values and associ- ated metal toxicities on the population structure of a given fish species. As previously noted, one of the primary mechanisms proposed to explain the loss of fish populations is the recruitment failure of a new year class. Field observations have been reported which indicate that acid stressed fish populations often have missing year classes.

Step 2 would enable estimates of population structure given a range of pH values. Step 1, while con- sidered analytically necessary for the performance of this judgement is obviously not sufficient. If Step 1 were - in the opinion of the participating scientist - superfluous, he could then directly perform the elicitation at Step 2. The third elicitation was designed to obtain estimates of population reduction in three lakes, and considered only direct effects on a single species.

The lakes initially con- sidered were Woods, Panther, and Sagamore. Each of these lakes is located within the Adirondack Park Region of New York State and receives similar acidic inputs. Of the three lakes, Woods is considered acidic typical outlet pH between 4 and 5 , Panther is considered neutral typical outlet pH near 7 , and Sagamore possesses an outlet pH which usually varies between that of Woods and Panther.

The characterization utilized for the initial eiicitation was based upon information published by Chen et al. Three lakes characterized by Dr. Charles Driscoll were also considered. No final decision was made at this stage of the project, as the selection of "representative" lakes was felt to require the assistance of the scientists selected to conduct the pretest and evaluation of the elicitation framework.

This third elicitation included considerations of natural habitat sensitivity. The uncer- tainty in estimates of the relationship between fish mortality and pH included, influences of lake morphometry, such as uneven mixing, temperature stratification, different inlet, groundwater upwelling, and outlet chemistries, pulse events, and lake turnover time. The step 4 elicitation was designed to elicit fish population decline within each of the three lakes incorporating both direct and indirect effects; e.

The careful specification of watershed geology, soil type, and lake morphometry in Steps 3 and 4 was considered necessary in order to: 1 present standard sets of data to the scientists participating within the elicitation; 2 partially reflect the range or variability of chemical, biological, and geological parameters of Adirondack watersheds; 3 provide some basis for a regional extrapolation of damages to fish populations; and 4 determine the significance of the variability between "bioassy results" and "lake estimations" for the assessment of regional effects.

Because a number of the scientists were more familiar with Adirondack water chemistry and fish populations than the remainder of the participants, a careful specification of the particular lakes under consideration was required. Identical data sets were required for the elicitation in order to prevent pos- sible errors or bias in the aggregation of the cumulative damage functions prior to the computation of regional effects. The lakes were to be selected so that they would be considered representative of a class of Adirondack lakes sharing similar water quality parameters.

The investigators originally intended to extrapolate from these three "representative" lakes to obtain estimates of the effects of changing pH records on fish populations for the Adirondack Mountain Region. However, this initial elicitation struc- ture was revised extensively prior to its application. The final elicitation structure made this extrapolation unnecessary. The initial elicitation structure is complex relative to the final elicitation structure.

After scientific review, it became apparent that while the initial structure, or something like it, would more explicitly address mechanisms of fish mortality than would a more simplified approach, that the current inventory data and time available for the performance of the project would not warrant the application of these more complex formulations. In addition, the detailed specification of the varia- bles in the initial elicitation made subjective estimates of the effects very difficult to perform with any degree of confidence.

Selecting the appropriate degree of resolution for the framework proved, in itself, a difficult interdisciplinary problem. This is sig- nificant for two reasons. First, it suggests that the selection of the variables for "regional" assessments of acid deposition effects should be a function of two considera- tions: the current state of scientific knowledge and the precision of other complimentary analyses.

Second, it suggests the continued importance of scientific con- tributions to the development and application of assessment "models". The initial elicitation was developed by the project investigators with only minimal dis- cussion with outside scientists.

The next steps consisted in: the presentation of the ini- tial structure for comments; a pretest of the elicitation in order to identify problems; and revisions prior to its actual implementation. Comments were. Before conducting an elicitation, a number of questions needed to be addressed. First, did the structure of the elicitation reasonably represent the estimation problem? Lastly, what information could be compiled that would help the scientists esti- mate the range of uncertainty around estimates of the effects of-pH on fish populations?

Several recommendations were made for improving the clarity of the presentation. The purpose of this meeting was to exchange ideas regarding the best method for eliciting the lower and upper bounds for the effects of pH on fish populations. Potential biases in the manner in which individuals estimate subjective parameters were considered, as were biases that could result from the way in which questions were asked or from the presentation of information during the elicitation.

In the initial elicitation framework the independent, or causal, variables were a given summer, surface pH measurement, assumed to be taken in the epilimnion, and related concentrations of total aluminum and calcium for typical Adirondack waters. The dependent variable was to be a percent reduction in a species fish population. Scientists were to consider differences in characteristics of Adirondack lakes in estimating the range of possible effects for a given pH, including size of the lake, possible existence of refuges within the lake; genetic variability in the susceptability of fish to pH depressions, and the likelihood that a lake with a given summer surface pH record would experience severe spring pH depressions.

Orie Loucks, Dr. Gary Glass, and Dr. In order to address these and similar questions, the project investigators prepared a memorandum for distribution to the selected elicitation participants outlining the following points: the need for the extension of scientific results to broader regions; the nature of the uncertainty implicit in such an extension; and the mechanism proposed by ERC to dimension this uncertainty.

It was decided to include a summary volume of a previous report which suggested application of this technique in order to dimension the uncertainty surrounding effects estimates, and a progress report outlining work performed on the project. Max Henrion of Carnegie-Mellon University was particularly helpful.

Many additional uncertainties were identified that affect regional estimates of the effects of pH on fish populations. While the investigators initially developed parameters -which "they felt necessary ito a regional assessment 3. Figure presents a revised intermediate elicitation structure. The revised structure represents a clear simplification of this investigators' original schema. While the output of both the initial and the intermediate eticitations remained the same, i.

Damages to both juveniles and adults were to be estimated in Step 2. Step 3 of the intermediate elicita- tion structure provided the same output as Step fr of the initial elicitation structure See Figures and The elicitation of the damage functions was to be performed over three different Adirondack lakes, Sagamore, Woods, and Panther.

Baker advised against the use of Big Moose, Little Moose, and North Lake, which were also being con- sidered, because they were less likely to be representative of a broad range of Adiron- dack lakes. Schofield of Cornell University is gratefully acknowledged. Baker worked with the project investigators for several days, asking helpful questions and offering suggestions for improvement. All three lakes are larger than ha. The geologic makeup surrounding all three lakes is similar, with the area being underlain by siliceous bedrock Driscoll, EUcitation over damages to reproductive life stages eggs, sac fry, fry 2.

EUcitation over damages to juveniles and adults 3. EUcitation over damages occurring in representative habitats. Three is based on set of exemplary lakes. As with the initial elicitation structure, the results of Steps 1 and 2 were not considered to be outputs for the regional assessment, but rather preparatory guides for the performance of the final, Step 3, elicitation. In addition to the above changes, the expression of aluminum levels as a function of pH for use in the elicitation was changed from tjhat shown in Figure to that shown in Figure Figure is adapted from Oriscbll and represents the concentration of inorganic monomeric aluminum as a function of pH.

Work by Baker and Baker and Schofield indicates that the species of aluminum present in dilute waters influences the toxicity of those waters to fish species. The final portion of the meetings consisted of a pretest of the elicitation interview process. Initially, it was hoped that the interview and technique would be sufficiently polished to allow for the performance of the intermediate elicitation.

However, because of a number of difficulties, the interview was not able to be completed. The output in the initial eiicitation structure was expressed as the percentage reduction of a given fish population within a lake. Because the data base maintained on fish in lakes by the New York DEC contains only presence-absence data for fish populations within the Adirondacks, the use of the elicited damage functions expressing change as percentage reductions of the fish populations within representative lakes was problematic.

To make the elicitation of the damage function expressed in Step 3 of the intermediate elicitation structure approp- riate, biomass or population statistics would heed to be developed for the Adirondack Region. The Morpho-Edaphic Index was considered as a possible mechanism for the prediction of fish biomass with the DEC data set. Many important insights were obtained from an actual dry run of the elicitation which were not apparent during the discussions of the procedure.

In addition, even if the ME! During these meetings no decision was made concerning the treatment of these ques- tions. It estimated the percentage of Adirondack lakes which could possibly, but no longer can, sustain populations of a parti- cular fish species at a given summer pH measurerr ent taken in the epilimnion. Thus, the dependent variable was changed from a measure olf the reduction in fish biomass or popu- lation to a measure of the reduction in a fish species habitat.

This change responds to considerations mentioned earlier, and reflects the general absence of inventory data expressing biomass or number of fish per -unit of measurement. Because a substantial gamefish stocking prograni exists in the Adirondacks, separate elicitations were felt to be necessary for stocked fcnd non-stocked gamefish populations. This adjustment was necessary because of different sensitivities of the reproductive and adult life stages to pH depressions.

Scientists were asked to estimate the percentage of Adirondack lakes which could possibly, but no longer can sustain both: 1 self-sustaining populations of a particular game fish; and 2 projperly stocked populations of juvenile and adult game fish. For non-game species, for example, white sucker, the sensitivity of only unstocked populations was evaluated. These were eliminated for two reasons. First, time required for the elicitation interview would be significantly reduced.

Second, the elicitation over the different life stages of the fish species did not, in the opinion of several scientists, significantly contribute to the third and most important elicitation result. The method proposed in the initial and intermediate elicitation structures required the extr- apolation of the elicitation results for three "representative" lakes to the entire Adiron- dack region.

While this procedure reduces uncertainty in the estimation of fish damages for the "representative" lakes, the extrapolation to the Adirondack Region would be done without the explicit dimensioning of the uncertainty by the scientists. Section 4. The first step was to compile a list of authors from the peer review litera- ture and government reports consulted by ERC during the literature review.

Weighting in selection was assigned on the basis of: 1 the number of recent publications; and 2 the amount of work performed in the Adirondack mountain region. On the basis of this initial review, a list of scientists was compiled. A number of Canadian scientists were included within the list of possible participants in order to provide a comparison between Canadian and American research communities.

The second step consisted in the contacting of possible participants and determining their willingness to participate in the study. During these initial phone conversations, the length of the proposed interview approximately four hours , the research area, and the information requirements of the project were outlined. On the basis of these discussions, the number of potential candidates was narrowed down.

On the other hand, a number of additional candidates were proposed by those scientists initially contacted. Table 4. The purpose of the discussion with Mr. As a result of conversations with Mr. Kretser, the investigators obtained the complete data file for the ponded waters within the Adirondack area. The discussions with Dr. Driscoll addressed; first, the general review of the project's scope and methodology; and second, a review of the water chemistry parameters being proposed for use in the study.

The mailing took place approximately two weeks prior to the elicitation. The purpose of this mailing was to introduce the approach and the project goals in more detail to the elicitation participants. The package included three separate documents: 1 A description of the meeting agenda and a brief explanation of the rationale behind this type of approach.

Relationships between pH and pCa and between pH and inorganic monomeric aluminum were also included. In some cases, however, participants supplemented this data by consulting their own sources during the course of either the pre-elicitation interview orjthe elicitation itself. While each of the meetings followed the basici structure outlined above, there were dif- ferences between the interviews.

These differences are attributable more to the dif- ferent information requirements of the scientific participants than any variability of methodological design or implementation on th4 part of the investigators. The principal point made during this seg- ment of the interview was that any decision to implement an environmental policy must be based upon a probability assessment of the odds of benefits monetary or non- monetary from the policy exceeding the costs of its implementation.

The purpose of the project was stated to be the construction and implementation of a framework which would allow scientists to participate in the direct extension of the results of recent scientific research into damage estimates useful for policy analysis.

Secondly, it was stressed that this was an evaluation of this approach for dimensioning and incorporating scientific uncertainty in estimates of the regional effects of acid deposition. Some time was spent explaining what the investigators believed were the principal advantages to the approach being utilized in the analysis.

The advantages expected are: o First, that scientific information is less likely to be misinterpreted when the uncertainty is directly and explicitly incorporated into the analysis; o Second, it was stressed that the subjective probability estimates which express the damage to environmental receptors in this approach are not point estimates, but express the damages as a range..

At this point, the consensus judgement was: Q an objective expression i. The length of discussion concerning the theoretical and general aspects of the discussion noted above varied significantly between the interviews. It was the investigators' inten- tion to cover as fully as possible, given time Constraints, the queries and responses of the participants. In one case, for example, the discussion centered - for some time - on the need to perform any regional quantitative assessments of the damage occurring as a result of acid deposition and its effects.

The interdisciplinary discuss the communication between scientists and and assessment of the information for ons that resulted were very informative. The discussion concerned the scope -of the eHcitartion and had several purposes: I to ensure that the participant understood what the variables repre- sented; 2 to outline the data compiled by the project investigators for use by participants in the elicitation discussed in Section 4. As noted in Section 4. The independent variable was pH.

However, recognizing the potential importance of inorganic monomeric aluminum and calcium in determining fish response to low pH values, regressions relating calcium and and inor- ganic monomeric aluminum to pH in Adirondack waters were used to incorporate these factors within the analysis. No other potentially toxic or mitigative metals were expli- citly considered. No elicitations were performed without incorporating the effects of monomeric inorganic aluminum and calcium upon the dependent variable.

However, neither manganese nor zinc have been found to be toxic to fish at concentrations found in acidic surface waters. Aluminum, however, has been found to be toxic to fish at concentrations as low as. Free aluminum ion or aluminum hydroxide forms have been shown to be more toxic than organic aluminum complexes.

The solubility of inorganic aluminum in acidic Adirondack surface waters is apparently regulated by some form of aluminum trihydroxide solid Driscoli, ; Baker, Bog, seepage, and eutrophic lakes can all be expected to have different capabilities to support a fish population given the same pH measurement. In addition, the presence or absence of ground water upwellings, episodic or pulse pH depressions, uneven water mixing the temporal and spatial variability of chemical species within the lake , acid neutralizing or acidifying inlets, and the biologic production of alkalinity are reported to be related to fish mortality within the literature.

Compared with the variability of the other components of the interview, its performance followed a standardized format. After some discussion of the question, the expert concluded that there was, in his opinion, no chance of a set of Adirondack lakes with a sumrjier pH of 6. As a result, 0 percent was entered in the low column. On the other hand, to establish the high end of the range, the 'investigator would ask the participant to consider the greatest possible impacts to the set of Adirondack lakes which both possess summer pH measurements of 6.

These lower and upper bounds were chosen to represent a 95 percent confidence interval. In this case, the assumed 95 percent confidence interval implies that there is a 2. Once the range of impacts for a given pH had been specified in the above manner, the participants were questioned regarding where within this range the actual outcome was most likely to fall. It was quite difficult to elicit responses regarding the most likely damage outcomes within the estimated range.

A procedure was developed which was acceptable to the scientists and still provided tome information on where the most likely outcome would fall. The procedure followed was to enter the mid-point of the range in the table; for example, if the range were 0 percent to 15 percent the mid-point would be 7. Upon entering the value for the mid-point, the participant was asked to indicate whether the percentage of lakes no longer able to sustain fish populations would be likely to lie above or below the mid-point.

In our example, at pH value of 6. Once the participant decided whether the impacts were1 likely to be above or below the midpoint of the range, an "X" was placed either above or below the mid-point in order to express this weighting of the probabilities see Table b.

The elicitation continued until estimates for ail the pH levels were developed. In many cases the participant felt that the incremental change of. S pH5. At that pH, the concen- tration of inorganic monomeric aluminum was estimated to be approximately. In some cases, the participants were so uncertain that they were unable to weight either the "high" or "low" interval.

In such a case, no weighting was placed on either side of the midpoint. Not all of the elicitations began at the highest pH values, 6. In a number of elicitations, participants elected to begin at pH values around 5. This is not sur- prising, because the majority of bioassay experiments, as well as anecdotal literature, note effects at a pH of 5. The investigators do not believe that this change in the procedure affected the estimated ranges.

Review and. Assessment of the Elicited Damage Functions The final step in the eiicitation interview consisted in a review of the range and weight which resulted from the eiicitation. During the review, the participant and the investi- gator examined the range of impacts listed at the different pH values.

If the participant believed that the estimates accurately represented his beliefs, no changes were made. On the other hand, if there were distributions which seemed inappropriate, then these were reconsidered and changed where appropriate. Often this amounted to the alteration. Following these revisions to the estimates, if sufficient time was available, the interview was closed with a brief discussion concerning the participant's evaluation of the approach and his confidence in the use of its results.

Table fc-6 presents the results of each elicita- tion. The data will be interpreted in Chapters 5 and 6. Section 5. There are a number of ways to interpret and use the estimates obtained from the elicita- tion. One way is to simply show the range of estimated effects. Since each expert esti- mated lower and upper bounds of effects, these can be used to dimension the range of effects due to a change in pH. If two additional assumptions are made, probabilistic estimates of damages from acid deposition can also be obtained.

It is important to recognize that both the use of a 95 percent confidence interval and a weighting are assumptions. There is no quantative or stat- istical justification for either assumption. However, a 95 percent confidence interval was felt to be reasonable since during the elicitation the scientists were asked to dimen- sion a range of potential effects so that, in their opinion, the actual impact would almost certainly lie within that range. Assuming that the range represents a high confidence interval is consistent with the way the elicitation was conducted.

The assumption of a weighting is more problematic since the scientists were not asked during the elicita- tion to determine what the relative probabilities were between the weighted and un- weighted segments. Whenever the scientists were asked to actually assign different probabilities to the different segments, they resisted making the estimate. It was felt that the simple weighting used in the elicitation pushed the limits of the scientists ability to dimension the uncertainty surrounding the effects estimates.

The scientists simply did not feel that they could provide reliable estimates of actual probabilities, but they felt they could indicate on which side of the range mid-point the actual outcome would most likely fall. Given that this was all the information that could be reliably obtained, the task facing the project investigators was to design a method that credibly used this sparse data.

Since the specification of a confidence interval and interpretation of the weighting are both assumptions, it is important to perform a sensitivity analysis around any selected values. Confidence intervals of 90 percent anld 80 percent were used along with a 95 per- cent confidence interval to test the sensitivity of the confidence interval assumption.

In addition to the weighting assumption, sensitivity analysis was performed using a and 5A weighting. These different confidence intervals and weighting assumptions were felt to bound the reasonable range of assumptions. The 95 percent confidence interval is quite a high con- fidence interval ie.

Conversely, the 80 percent confidence interval was felt to be a lower bound. The results of the sensitivity analysis are shown in more detail in Appendix A; however, it was found that the assumed confidence interval had a significant effect on the damage estimates, but the assumed interpretation of the weighting had a minor impact. This is an important finding since the interpretation of the weighting is the most uncertain assumption. Further, this result justified the emphasis placed on obtaining accurate esti- mates of the potential range of effects while settling for a simple weighting scheme to indicate where within this range the most likely outcome might fall.

Example 1 Assume that for fish species X and a pH of 6. Assuming a 90 percent confidence interval and a weighting results in the cumulative distribution shown in Figure Example 2 Assume that for fish species X and a pH of 5. Given this cumulative probability distribution, the fol- lowing holds true: 30 equals. A weighting results in probabilities of. Recall that the estimate of the number of lakes damaged was found, in this application to be relatively insensitive to the weighting interpretation.

This section will outline the steps in the estimation of damages from acid deposition based on the elicitations. A simple illustration of these steps and a presentation of results from a test case sensitivity analysis of the confidence interval and weighting assumptions can be found in Appendix A. Table 5. Step One is the calculation of aggregate cumulative probability distributions of damages for each species of fish at each pH level. For example, five elicitations were conducted for self sustaining populations of brook trout.

The five different self sustaining brook trout elicita- tions were combined to form aggregate cumulative probability distributions of damages at each pH by first calculating cumulative probability distributions for each scientist's elicitation and then averaging the distributions. A computer program using simple numeric techniques was constructed to perform these computations. Step Two involves determining the present distribution of pH levels across Adirondack lakes.

This data base and others used are described in Section 5. Step Three is the presentation of a hypothetical case used to derive the change in the distribution of pH values caused by increases or decreases in acid loading. Step Four is the calculation of the incremental damages from the shift in the distribution of pH values calculated in Step Three. This is a conditional probability calculation. It is the probability of incremental damages given the current distribution of fish habitat in the Adirondacks.

Step 2: Obtain current distribution of pH values for Adirondack lakes. Step 3: Derive the change in the distribution of pH values across Adirondack lakes caused by increases in acid loading. Output: Given a predicted change in the distribution of pH values across Adirondack lakes, a cumulative probability function of the incremental number of lakes expected to be damaged.

To calculate this combined distribution, the distributions of damages to lakes segmented by pH class must be convoluted i. Referring back to Figure , the figure shows the probability distribution of damages if or a fish species in lakes with a pH of 6. A similar distribution could be graphed for lakes with a pH of 6.

The assumption of perfect correlation between these two distributions would mean that if actual damages at a pH of 6. In terms of the cumulative probability distributions, this means that if the actual damage outcome turns out to be that outcome associated with a. The assumption of perfect independence implies that finding high levels of actual damages in lakes with one pH does not change the probability of high or low damages in lakes at neighboring pH values.

Instead of assuming perfect correlation or perfect independence, a compromise assump- tion of partial correlation between distributions is possible. With partial correlation, a high damage outcome at one pH level does not imply a high damage outcome at a neigh- boring pH level, but it does imply that the probability of high damages at the neighboring pH levels increases. The assumption of perfect correlation results in the most uncertainy i. This stems from the fact that, with perfect correlation, if damages at one pH turn out to be very high, the damages at neighboring pH levels will also be very high.

Thus, extreme values are always coincident. This tends to increase the probability that actual outcomes will fail in the tails of the joint distribution. However, it does not change the upper and lower bounds of the distribution. Thus, the assumptions of perfect correlation and perfect independence can be used to bound the uncertainty. The appropriate dependence assumption was discussed with scientists during the pretest phase of the project. The scientists indicated it reasonable to assume that if actual damages at one pH level were in the low part of the distribution, then actual damages at neighboring pH levels will also be in the low portion of their distributions.

This implies that underlying factors which make estimates of damages uncertain are correlated across pH levels, and that if scientists learned that actual damages caused by pH 5. For this study, perfect correlation was assumed. This assumption provides an upper bound to the uncertainty in the estimates and it is mathematically much easier to work with than partial correlation. By assuming perfect correlation, it is possible to sum calculated distributions of damages across different "clusters" of lakes to obtain total distributions of damage to lakes.

A "cluster" of lakes is a set of lakes that have the same current pH level and the same ending pH level after the shift in pH levels. Appendix A presents a simple example of these calculations and the results of a "Test Case" sensitivity analysis of the weighting and confidence interval assumptions. This is incorrect. The assumption of perfect correlation implies nothing about the placing of weights during the elicitation. The scientist place the weights in the manner they feel most appropriate.

Assumptions of correlation or independence influence how the resulting distributions are combined. Published and unpublished data provided by a number of othelr investigators were also used. These in- cluded data collected in by Dr. Carl Schofield unpublished data ; a characterization of Adirondack lakes provided by Dr. This section will describe salient charac- teristics of the DEC data as it was represented on the Adirondack Waters Management System Tape, as well as the manner in which the data were interpreted and used in a regional assessment of fish damages.

To sort the data into meaningful units for analysis, the variables in Table were reorganized into a working data base. The data base is not entirely com- prehensive, as not every ponded water has a complete record. For example, while there are a total of pH records within the data base, only of these are contained within the Chem-Current File the file containing most current chemistry survey data for those waters which possess chemistry surveys.

Similarly, while there are a total of alkalinity records for Adirondack ponds, only are contained within the Chem- Current File. The pH measurements were obtained with a'pH meter under air-CO2 equilibrium condi- tions. In the initially published results, 25 percent of the surveyed waters registered pH readings below 5. There were a total of 'records for calcium and for magnesium within the Data Base. Record type 2. Watershed 3. Date Recorded Date of Samples Depth ft.

Measurement Method Remarks W. Source Sample Type 2. In order to compare current levels of acidification with these historical records, the investigators recorded the current pH values using both a pH meter and a Hellige comparitor. In reporting the results, Pfeiffer and Festa showed that the colorimetric Heilige comparitor readings were consistently higher than the pH meter determinations see Figure However, when Schofield compared colorimetric measurements to meter pH measurements, he concluded that the agreement between the two methods was much closer than stated by Pfeiffer and Festa.

Schofield concluded that the pH meter determinations reported in Pfeiffer and Festa were between. Hence, the pH deter- minations for the ponded waters sampled in are probably between. The investigators have been unable to determine what percentage of pH listings recorded by the DEC and listed in the data base are in error. In order to assess the potential bias in data base pH records, a regression developed by Schofield relating pH to pCa was used by the investigators to determine the pH of the Adirondack waters for which both pH and calcium data were available.

The mean listed pH value for the sample was 6. The standard deviation of the pH values was. While the difference between the two values is important, the investigators didn't believe it to be large enough to justify not using the pH records contained within the data base.

The seasonal variability of the pH within individual lakes caused by biologic production, snowmelt, and in some cases, fall rainstorms, is probably equal to or greater than the variation expressed in the calculation of the lake pH values. Figure demonstrates the considerable variation in the pH of one Adirondack lake's summer-ice free-surface pH values. Readers, however, should be aware of this systematic bias in the characterization of pH values in the data base used in this analysis.

It possesses a well-defined inlet and outlet. All of the fish species for which damage elicitations were performed are included the Data Base. A data sort was per- formed to establish an inventory of Adirondack lakes posessing both chemistry records and presence-absence data for fish populations. Figure illustrates the sort pro- cedure. Of these, possessed fish records,. Records dated from to the present were considered current or indicative of the present pH and fish population status.

Of the examined, were surveyed prior to Assuming some change in the pH of those 2SO lakes between and the present indicates that our data probably over- estimates current pH and fish populations status within the region. There has been no published estimate of the rate of acidification in the Adirondack Region between and the present, but W. Watt et al. In searching the files for a pH record, the algorithm also looked for calcium and alkalinity records.

Of the lakes with pH records, there were which did not possess alkalinity records. Step 2 calculated the pH range of the ponded water's pH value. Lakes were assigned one out of 42 possible pH ranges. Increments of ,1 pH between 8.

If there was no record, or if the elevation was blank, the elevation class was set equal to "unknown". High elevation lakes in the Adirondack Mountain Region have been noted to possess both depressed pH values and reduced fish populations Pfeiffer and Festa, ; Schofield, b, , In a survey of lakes above feet, Dr. In , an additional 35 lakes were surveyed.

Is there an elevation record later than ? If so, calculate elevation class. If not, or if elevation is blank, set evaluation equal to "unknown". Is there an alkalinity record later than ? If so, calcualte alkalinity class. If not, or if alkalinity is blank ,set alkalinity class to "unknown". Is there at least one fish species record later than ? YES Read all job species records with the same data as the most recent one and set flags for each of the six species being looked for.

Add 1 to total for each fish species found broken down by alkalinity, pH range, and elevation class. Add 1 to total for all fish species broken down by alkalinity, pH range, and elevation class. Add 1 to total for all takes broken down by alkalinity, pH range, and eleva- tion class. Fish surveys conducted at the same time indicated that 82 percent of these acidic, high elevation lakes are devoid of fish.

If there was no alkalinity record, the alkalinity record for that lake was set equal to unknown. After assigning the lake to a pH, elevation, and alkalinity category, the program recorded which, if any, of the 6 species of fish for which elicitations were performed were present within the lake either in or later. A summary of this data, not includ- ing elevation and alkalinity records, is shown in Table Table contains a summary of the data excluding pH categories for the Adirondack Mountain Region.

There were no records of brook trout lakes below pH 4. Of the 2, lakes which comprise the Adirondack Ecological Zone, only , or 34 percent, have been entered into the data base. According to the DEC unpublished data , the average size of the ponded waters in the Adirondack Ecological Zone is The DEC cal- culated the remaining unsurveyed ponds to have an average size of approximately The majority of these smaller ponds are found at high elevation sites on generally more sensitive soils, and, consequently, can be expected to have, on average, lower pH values than those ponded waters contained within the sample constructed for this analysis.

ERC implemented a separate sort algorithm in order to differentiate between those waters containing stocked and naturally reproducing populations of brook trout and lake trout. The results of that sort indicated that there were a total of 77 lakes with stocking records and recorded brook trout populations after Of these, he records that approximately ponds, representing some 12, acres, receive annual stocking with fall fingerling wild x domestic hybrids.

Pfeiffer predicts that "about 25 percent of the existing viable acreage will succumb to acidifiction by However, in a recent personal communication, Pfeiffer indicated that there had been a slight improvement in the condition of brook trout ponds since the beginning of monitoring in He indicated that, while the pH of ponded waters in central and western New York had declined over the period, that the pH had increased slightly in eastern and southern New York.

Pfeiffer lists ponds within the Adirondack Ecological Zone as being stocked with brook trout. The DEC confirmed that at present, many stocking records have not been entered on the data! Damages to stocked and unstocked habitats were estimated. The Data Base was further analyzed into the six drainage bases which jointly constitute the Adirondack Region. The results of this sort are represented in Table Elevations apparently strongly influences alkalinity.

This compares with 1 percent of the lakes above feet. Table represents the same terrain, according to the calcium level of Adirondack lakes analyzed by elevation and major drainage basin. While direct comparison between i Tables and is difficult, the general trend of increasing alkalinity values and cal- cium values with decreasing elevation is evident in both.

There are an additional 33 private lake trout waters, which Pfeiffer assumes have self-! NO K The base additions can be taken to represent either reductions in the input of acidic deposition; or, presuming no change in the level of acidification, a mitigation strategy of base addi- tion.

It asumes that all Adirondack lakes have the chemistry outlined above, provides no time rate of change for the aquatic chemistry, and makes no attempt to relate the change in aquatic chemistry to changes in the rates or concentrations of acidic deposition. In order to calculate the change in pH, two computer runs were executed.

The first fixed or esta- blished the pH at values from 4 to 8 in 0. The model then calculated the amount of acid or base required to shift and fix the pH values at a new steady state. The model calculated the extent of change in the pH of lakes relative to the fixed pH values along the bottom axis of the graph. The results of the runs are shown in Figure Changes in lake pH represented in Table were calculated using Figure Notice that the buffer intensity of the system seems weakest in the pH values ranging from approximately pH 7 to pH 6.

Lakes below 4. At pH 4,5 and below, the model results were highly variable due to the in- creased aluminum buffering in the system. However, lakes with pH records equal to or below 4. He attributed this to the hypothesis that, for Adirondack waters, this was the region of minimal buffering intensity.

The model runs depicted in Figure indicate, however, that there is less buffer intensity between pH 7 and pH 6. The model runs indicate that the Adirondack lakes are strongly buffered by the aluminum system rather than the carbonate system. In a carbonate buffered system, the maximum buffering intensity would occur at pH 6. As discussed pre- viously, while the aluminum buffering systeijn prevents or slows down further lake water acidification, it tends to stabilize the systjem at very toxic conditions due to the re- sultant combinations of pH and aluminum levels.

There are 10 records of fish populations in water with pH less than 4. Ninety percent of those low pH lakes contained brook trout, one contained white suckers. For example, for a lake with a pH of 6. The lake would shift from a pH of 6. Results for brook trout and lake trout are expressed both for stocked and self-sustaining populations. The computations of incremental damage were made using the following assumed parameters: 1. Three of the four lake pH shifts calculated using the model described in Section 5.

The second section presents the results of a base addition scenario which would result in the increase in pH of the cluster of lakes. A slightly different procedure was used to examine the effects of base additions to the lakes. The third section presents a comparison of the response of the different fish species habitats and an evaluation of the results using two different cal- culation procedures. Both of these scenarios represent rather large increases in acid deposition. Based upon this estimate, the two scenarios represent roughly a 50 percent and a percent increase over present levels of acidification from antropogenic sources.

The damages range from a lower bound of 4,7 lakes, or approximately 1. The median value is Because the results represent a cumulative probability distribution, the median represents the number of lakes which divides the range of probabilities of damages into two equally likely seg- ments. The expected value of damage is the mean of the probability distribution. If the mean, as in this case, is less than the median value, the marginal probability distribution representing the shift would be skewed towards the lower end of the probability range.

Conversely, if the mean is greater than the median, the expected changes in the marginal distribution would be skewed towards the upper half of the range. The results expressed in column one indicate that there is a 10 percent chance that damages occurring to the sample of brook trout lakes would be equal td or less than S Jakes. Another way to use the information contained in the cumulative probability distribution is to calculate the probability that damages,from the shift in distribution of pHs across Adirondack lakes exceed a given level.

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Graham Soil and Water-Vol. FL ,IJ. Sartain Soil and Water-Vol. Ordinarih, contributions shall h,1,c been presented at lutrients in Citrns Production Svstell! He, D. Klock-Moore and G. Li, Pf. Stofjrlla, and H. AdJl'i, i. Gmdne,; D. Jm11ing1 tt mato in Compost-. IL ;mh! P Mis[n. Melessl'and S. J cript is a carry-over. Business 'vlecting 2'. Board of Directors Meeting '. Society Banquet and.

Honorary Lifetime Memhns List of Dedication of l'roceedi11g, William H. Pritchett DR. William L. Pritchett, retired professor of Forest Soils at the Univ. Pritchett was born on 17 Sept. He received his B. Colonel in Pritchett began his academic career as an assistant professor of Soil Chemist1y at the Pniv. In El! Over the course of his second stay at the Univ. Bahamas; Univ. As one of the early southerll researchers investigat i 11g soil fertilit, problems in corn rnercial forests, Dr.

Pritchett was a co-founder of the :ooperative Research in Forest Fertilization CRIFF program, which over its life was responsible for the education and training of 43 graduate students and five post-docs, and produced nearly ' professional publications. The culmination or his work was the textbook 'Properties and Management of Forest Soils". The book has been translated into more than '20 larnmages and is used worldwide.

PAGE 6 Dr. Bullard Fellow in , he was given the opportunity to begin work on his textbook. Instead of retmng quietly in , Dr. Fol lowing his retirement in , Dr. Pritchett continued his profile writing by producing a family genealogy ancl writing an autobiography. Bill Pritchett will be missed by the many people whose li,es he touched. In recognition of his contribution to science, to Florida's f edings to the nwmory of Dr.

He served for 4 yr in the L. Coast Guard and later enrolled at the Univ. He began his work in nematology under the supervision of Dr. Chitwood, an eminent scientist considered to one of the founders of the science of nernatology. Chitwood's guidance, Dr. Esser learned the many aspects of nematology. Esser became deeply involved in regulatory nematology as part of the mandate of his agency.

His contributions and experience relating to nematode pests of citrus, in particular Radopholus similis, the burrowing nematode that causes spreading decline, made him one of the most highly regarded experts worldwide in regulatory nema-tology. The numerous regulatory and sanitation manuals he has prepared and published are widely used in Florida and in other states and countries.

He has described several new species of nematodes, including Verutus volvingentus, an ancestral form of the cyst nematodes, and the subject of his Ph. He developed an innovative, comprehensive nematode taxonomic database by encoding all the spe cies of plant parasitic nematodes described to the present time. He possesses one of the most complete literature filing systems related to nematode taxonomv in the countrv. Although nematology is an integral part of Dr.

Esser's life and career, he is often involved in other aspects of regulatorv and plant protection activities or the DPT. For example, he was recently DPI's representative for the FDAC Compost Task Force, in recognition of his expertise in regulatory and safety issues involving the spread of harmful organisms. A number of his more than national and international papers were published in the Society Proceedings, including several taxonomic compendia, nematological surveys, protocols for regulaton methods, and papers dealing with soil zoology, nematode-host relationships, and in particular natural control agents or nematodes and other organisms.

Calvert Optimal management of nutrients and organic amendments is very important for improving crop production to meet the demand for food and fiber by the rapidly expanding world population while minimizing the negative impacts on the environment. Nutrient and organic amendment management depends on balancing soil nutrient status and nutrient inputs with crop requirements and environmental considerations.

Because of time, this symposium was limited to consideration of management of nutrients and organic amendments applied to citrus, ornamental, and vegetable crops. How ever, similar management strategies need to be devised for all Florida crops and should include management of nutrients and organic amendments in parks, forests, golf courses, pasture, nurseries, and highway right-of ways, as well as urban and rural lawns.

This symposium was organized to a present current scientific information and b to provide practical experiences on the management of nutrients and organic amendments in specific crop production systems. Information from this symposium indicates that in many areas of Florida varying quantity and quality of water supplies limit nutrient use-efficiency, especially where there is increasing competition for water among agriculture, urban and industrial users.

Additionally, this symposium provides the reader with current knowledge on the type and levels of nutrient loads that can be assimilated by water bodies without exceeding water quality standards. It also briefly examines the economic importance and environmental impacts of developing efficient crop production systems. For several site-specific production systems, the papers presented in this symposium address the roles and importance of current research and development on management of municipal sludge biosolids , composts, and farm manure poultry in cycling nutrients and maintaining soil fertility.

He"', D. Calvert, A. K Alva, and Y. Fertilization and irrigation play important roles in the sustainable production of citrus. Because of increased concern over water quality, improved agricultural practices to increase nutrient utilization efficiency and to minimize nutrient loss are required. Citrus Citrus spp. From the s to the early s, studies were conducted to understand the effects of fertilization on yield and quality of citrus.

The information and knowledge generated during that period are still useful in guiding current citrus fertilization practices. Since the introduction of irrigation practices in the s, the interactions of irrigation and fertilization on citrus production and water quality have become a major focus of research. Studies on best management practices BMPs in the s has added more to our understanding of citrus production with regard to water quality as affected by water and nutrient management.

Progress also has been made in the development of optimized fertilization programs to enhance citrus production and to minimize impact on water quality. Citrus production began in Florida about yr ago, and citrus fertiliz,1tion pr,1ctices can be u-aced back to the late s Moore, In the early s, low analysis fer tilizer and organic N sources were used Putney, ; Ruprecht, Effects of fertilizer rate and sources on fruit vield and quality of citrus were conducted during s through s Calvert and Reitz, ,1; Reitz and Huruiker, l 9ti l; Reitz and Koo, ; Reuther and Smith, ; Sites et al..

Management of nutrients and irrigation has been greath imprmed since then and has played a crucial role in enhancing citrus production and improving citrus fruit quality in Florida. Calvert, Univ. Indian Riv,-r Res. Li, Uni,. Soil Crop Sci. Most of the soils used for citrus production in Florida are sandv, with inherently low fertilitv due to the low holding capacities for nntrien1s and moistnre within the rooting zone Calvert, ; He et al. Nutrit'nt management needs to focus on minimizing the impact of fertilization and irrigation on drinking water and environmental quality.

Minimizing the losses of nutrients which become sources of non-point pollution of water, requires a sound understanding of phvsical, chemical, and biological processes related to transformation and transport of nutrients within the vadose zone and optimal management of irrigation.

This required renewed attention to the optimal management of N and irrigation in , effort lo minimize leaching losses. This is par ticularly important in Florida because most soils are sandy with low nutrient holding capacities Tucker et al.

Significant yield increase since the iOs is, in part, attributed to increasing amounts of fertilizer ap plied. Among all the essential elements for citrus growth, N is considered to be the most important and recciH'S the most attention and research Davies, Therefore, the aim of nutrient management is to both minimize NO, leaching below the rootzone and to attain maximum economical prod11ction.

Balanced nutrition is important to support high yield and quality of citrus. Accordingly, an N:P:K ratio of I The fertilizer rate effect on fruit yield generally fol lows a quadratic relationship AlYa and Paramasivam, ; Calvert ct al.

An example of the above relationship is shown in Fig. The results of some important studies are summarized in Table 1. In general, on a unit-area basis, the optimal fertilizer rate is greater for oranges C. These rates are somewhat greater than the recommended N rates; i.

With recent trend towards high density planting and considerably greater fruit yields ha-1, the N required kg-1 fruit could be somewhat lower than those reported previously. With intensive production practices, fruit yields of up to 70 Mg ha-1 are not uncommon.

On the basis of the above N requirement guidelines, the N rate required to support 70 Mg ha1 would represent around and kg N ha-1 yr1 respectively, for oranges and grapefruit. However, current fertilization practices are well below these rates. This increased efficiency of N use in the recent years can be attributed to improved management and scheduling of irrigation and fertilization Alva and Paramasivam, Fruit Quality Fruit quality affects economic returns, especially for the fresh fruit market, and therefore is an important component of citrus production.

The amount of N required for maximum or optimal yield of citrus fruit. In general, increasing N rate tends to: l increase juice volume, total soluble solids TSS , acid content, and juice color; 2 increase number of green fruit at harvest and incidence of creasing and scab; and 3 decrease fruit size, weight, and peel thickness.

Increasing rate of P decreases acid content, increases Brix:acid ratio and number of green fruit, reduces peel thickness, and increases expression of wind scar. Increasing the rate ofK decreases injuice content, solids, Brix:acid ratio, and juice color, while increasing fruit-acid content, fruit size, weight, peel thickness, and green fruit number Boman, ; Calvert, , ; Calvert and Reitz, ; Embleton et al.

There are strong interactions among N, P, and K with respect to their effects on fruit quality. For instance, the effect of increasing N application on fruit size may be countered by simultaneous increase in K rate. An increase in N rate is accompanied by a proportional increase in P and K. The effect of fertilization on fruit quality is a comprehensive result of N, P, and K interactions.

Therefore, it may be more meaningful to examine the effects of fertilizer rate rather than the amount of individual nutrients on fruit quality. A summary of effects of fertilizer rates on fruit qualities of White Marsh grapefruit is shown in Table 2. When using a mixed fertilizer blend containing N:P:K ratio of Peel thickness, which is related to fruit size, declines at higher fertilizer rates Table 2.

Therefore, if a large grapefruit is desired, an N rate kg ha1 yr1 with. A systematic report about effect of fertilizer rate on orange quality is not currently available. However, similar results are expected regarding the effects of fertilizer rate on fruit size and peel thickness of oranges.

Increase in N rates from 0 to kg ha1 yr1 increased TSS and fruit-acid content of grapefruit Table 2. The fertilization rate effect on fruit Brix content was more complicated. Brix content was not affected by N rate in the range of O to kg ha1 yr1 but increased bv increasing N rates from to kg ha I yr1 Therefore, the Brix:acid ratio generally decreased with N fertilizer rates Table 2.

The philosophy of BMPs is to maximize nutrient uptake by minimizing various losses. This will maximize economic returns and minimize residual nutrients in soil susceptible to leaching loss. Citrus trees with low nutrient status usually have higher nutrient uptake efficiency than trees with high Table 2.

Effects of N fertilization on fruit quality of White Marsh grape fruit. J:P:K 1 For mat. Nutrient Removal by Harvested Fruit The percentage of nutrients removed by harvested fruit compared with the total amount applied can he a measure of nutrient uptake efficiency for mature citrus trees. The amounts of N and K removed bY harn. Critical concentrations of N, P, and Kin 6-mo-old spring flush leaves needed for optimal yield of citrus.

Relative fruit yield of the grapefruit was, however, q naclratically related to leaf N concentration Fig. For P and K, the critical leaf concentrations were 1. These standards are in close agreement with those proposed by Reitz and Hunziker Fertigation, Controlled Release Fertilizer Source vs. Water Soluble Granular Form Water-soluble granular fertilizer has been the major form of fertilizer used by the Florida citrus industry.

These results suggest nutrient uptake efficiency may be greater with fertigation as compared with the application of water-soluble granular fertilizers. Controlled-release fertilizers contain one or more plant nutrients in a form that either delays nutrient availability or extends its availability Mortvedt and Sine, Controlled-release fertilizers applied in part or throughout a fertilization program have been observed to significantly reduce N leaching in citrus cropping systems on sandy soils in Florida Alva and Paramasivam, ; Wang and Alva, Greater tree growth and fruit yield have been reported using controlled release fertilizers as compared with water soluble granular fertilizer Boman, ; Alva and Paramasi vam, ; Obreza et al.

A recent study by Obreza et al. However, because of its greater cost, the economic feasibility of using controlled-release fertilizers for citrus production needs to be further evaluated. Table 5. Increase in fruit yield by fertigation as compared to that with broadcast of watersoluble grannlar. In another study in west central FloricLt, occasionally NO,-N concentrations in groundwater were observed to exceed 10 mg L', even at 3-m depth below land surface on flatwoods soil McNeal et al.

The potential for nitrate leaching is greater in ridge areas of deep sand in central Florida. Solution P04 -p concentrations at the cm depth average 0. Soil water above this depth mav seep into water furrows through lateral rnovcment and be discharged into surface drainage water He et al.

A column leaching study conducted by He et al. The argillic horizon had much less effect on tlic nTtical transport of NO 1-N along the soil profile He et al. Cnder field conditions, the denitrification process mav be an important mechanism that keeps NO, concentrations at rela tively low levels in the flatwoods soils, as denitrification generally increases with the availability of NC , and or-Table 6. The potential maximum NH. JO, g kg Ammonia volatilization was minimal at soil pH of 3.

The potential maximum T',,;I L, volatilization increased by 2-and 3-fold, with an increase in temperat11re from 5 to 25C. The greath' enhanced NII, volatilization at 45C:, as compared with that at 25C, was related to the inhibition of nitrification at the high temperature, which incrc. Under field conditions in a citrus grove I 00 to g kg-1 N loss by NH, volatilization measured using sponge-tracking techniques was also observed ParamasiYam et aL, Application of cellulose increased the microbial biomass, thus enhancing immobilization of applied N and decreasing volatilization loss.

The effect of CZ appears to be related to increased retention or NH,' in the cationexchange sites. The strong positive interaction between cellulose or CZ amendment and microbial biomass resulted from improved water and nutrient retention in the soil and availability to microorganisms. Best management p1actices for irrigation and frnilization of flol'ida citrus in Flatwoods soils. Project Completion Rep. Contract No: 93W , Fla. Soil Sci. Plant Anal. Alva, A. K, and S. J l:i Impact of nitrogen management practices on nutritional status and yield of Valencia or:1nge and ground waler nitrate'.

J Environ. Boman, B. J A comparison of controlled-release ru convent ion al fertilizer on mature 'Marsh grapefruit. State Hort. Homan, B. Effects offrrtili1ation and potash source on grapefruit size and yield. Fertilization, Israel Inst. J G. Fertigalion ,ersus conn,ntional fenilization o! Flalwoods grapefruit.

Calvert, D. Effects of rate and frequencv of fertilizer applications on growth. Response of "Temple" oranges to varying rates of nitrogen. S1ate Hort. Nitrate, phosphate, and potassium movement into drainage lines under three soil management svstems. An evaluation of grapefruit leaf nutrient concentrations vs. Aha, Y C. Li and D. In Agronomy abstracts. ASA, Madison. Soil :me! Crop Sci. Florida Proc. J Reitz. A fertilizer study with Valencia oranges in Lhe Indian River area.

Ell'ccts ol r. Li, and D. Llfects of nitrogen krtilization ol"grapefruit trees on soil acidification and nutrient availability in a Riviera fine sand. Plant Soil I J Hutchinson, C. Science iEi. Koo, R. The influence of N, K, and irrigation on tree size and fruit prnduction ol 'Valencia orange.

Results of citnis fertigation studies. Tucker, D. Recommended fenili1 " Ruprecht, R. Citrus fertilizer expnirnents. State 1 lort. The rate and timing of nitrogen for grapefruit on Lakeland fine sand. Hochmuth ABSTRACT Vegetables are produced on nearly acres ha in Florida and fertilization is important for profitable production of high-quality vegetables in this state.

Optimum management of nutrients for vegetable production is important for several reasons. Secondly, nutrients, such as N or K can be mobile in the sandy soils of Florida and this is a particular problem under heavy rainfall or excessive irrigation. Finally, nutrient management is important because nutrients lost to the environment can negatively impact the quality of ground or surface waters.

Vegetable growers have several technologies within their reach to maximize nutrient management, including calibrated soil testing, polyethylene mulch, fertigation, controlled-release fertilizers, and plant tissue testing, among others. In addition to these technologies pertaining directly to nutrient management, growers have new information on optimum irrigation management at the farm level.

Water management on the farm is critical to successful nutrient management. Commercial vegetable producers in Florida face many challenges for profitable crop production. There are severe economic challenges, including competition from other countries as well as intrastate competition.

Costs of production co11tinue to rise. There arc cstant pressures from new insect and disease pests. Each of these new pests requires new crop and pest management strategies to minimize the negative impacts of the new pest. Farmers face continual risks from nature, including freezes, floods, and droughts, all of which cause crop losses and add to the costs of production. These laws add more costs to the farm for compliance. Fertilizer management is important for successful yegetable crop production, but scyeral issues impact how fertilizer is managed on the farm.

Concern over nutrient contamination of the environment has led to interest, on the part of governmental regulators, in the implementation of best management practices BMP on the farm. A nutrient management BMP can be thought of as an integrated system for supplying nutrients for economical crop production and which maintains environmental nutrient standards. The pollution issue is particularly acute in southern Florida with G.

Hochmuth, North Florida Res. Center and Horticultural Sciences Dep.. Florida Agric. Journal Series No. Moreover, recently it was documented that insect populations and damage can be enhanced with excessive N Funderburk et al.. One of the most important factors in optimum nutrient management is knowledge about crop nutrient requirements for the yegetable being produced. Often, fertilizer alllounts are set based expected yields.

As fertilization rates increase, yield will increase to a certain point, after which more fertilizer onlv leads to fertili7cr being left behind in or below the root zone. These nutrient requirements art' the result of significant research with vegetables, in some cases, for more than 50 yr.

Recently, the vegetable fertilization literature was summarized for 11 vegetables Hochmuth and Cordasco. This sun ev of' 1. Calibrated soil testing is used to determine the part of the crop nutrient requirement that can be supplied hy the unfertilized soil. Many commercial and public labs are available for soil testing, but not all can reliably interpret test results for soils in Florida.

Growers need to choose a competent lab that uses soil-testing procedures calibrated for Florida. There are several philosophical approaches to making fertilizer recommendations, causing confusion among soil testing lab clients Olson ct al. Onlv the percent suHiciency approach to making fertilizer recommendations should be used in Florida. This approach makes a fe:Ttilizer recommendation taking into account the amount of crop available nutrients already in the soil.

Fertilizer might not be recommended when the soil already contains enough nutrients for optimum crop production. The calibration is especially supported for I' but less so for K. The mobility ofK is tht' main reason for the poorer calibration, compared Lo P, Soil testing for N is not calibrated in Florida because N is very mobile in the sandy Florida soils, and N fertilizer needs are difficult to predict based on a soil test, Once the fertilizer amounts have been determined, nutrient.

For most Florida vegetables, a combination of preplant and postplant applications offertilizer are needed. The reason for this is that fertilizer is subject to leaching losses, especially the mobile nutrients N and K. Most research shows that P should be applied to the soil in the bed area before planting. Tomatoes Lycopnsiron esculentum! The preplant-applied N and K should be incorporated in the bed area.

For 1nany vegeta bles, polyethylene rnlllch protects mobile nutrients from leaching and could be considered a component of a nutrient management BMP Hochmuth, Controlled-release fertilizers have been shown to have positive effects on vegetable yields in Florida Lo cascio ct al. Selection of nlltrient sources should be made based on nutrient content and cost factors. Research has shown lhat the source of soluble Nor K rarely affects vegetable crop performance Locascio et al.

Cook and Sanders. Nitrogen and K fertilizer should be injected according to a schedule based on crop growth and nutrient demand Hartz and Hochmuth, ; Hochmuth, a; b. For unrnulched crops, the remaining N and K fertilizers art' applied to the soil in bands near the crop in two or three applications during the crop growing seasons. For crops grmring on mulch and drip irriga tion, the N and K can be injected through the drip system in amounts according to crop growth.

Schedules for N aml K injection into drip irrigation systems have been published for vegetables in Florida Hochmuth, a; Hochmuth and Smajstrla, Research result5 have shown that rarely will vegetables respond positively to more than 3 kg ha1d-1 Hochmuth, For mulched crops without drip irrigation requiring applications of nutrients during the season, the liquid fertilizer injection wheel can be employed Csizinszky et al.

The most important factor in optimum fertilizer management in Florida is water management. Excessive irrigation or he,ny rainfall can leach N and K from the soil, leading, in the case ofN, to negative environmental impacts. Irrigation should be scheduled to maintain soil moisture potential near -8 to cb kI'a Clark et al.

Amounts of irrigation water should be determined based on pan evaporation measurements Clark, ; Smajstrla and Locascio, El The goal is to employ an irrigation program that results in maintaining the water and nutrients in the root zone. Nutrients lost from the root zone are suhject to movement into the groundwater. Plant tissue testing can be used to fine-tune fertilization programs or to diagnose suspected nutritional problems Hochmuth ct al.

There are two basic systems to use Cor plant tissue testing, standard laboratory analyses based on dried whole-leaves, and fresh petiole sap testing Ilochmuth et al. Petiole sap analyses are especially useful for vegetahles growing on mulch and drip irrigation Hochmuth, ; Rhoads, ; Rhoads et al.

Based on petiole sap analvses, small adjustments can be made in the injection schedule. Research conducted in Gainesville and Quincy, FL showed that there is an optimum time in the growing season for adjustments to the :injection of N for tomato Locascio et al. Vegetable production in Florida requires sig11ificant amounts of inputs for profitable production of high-quality vegetables. Fertilizer is one ol these required inputs. Proper management of the nutrients used in vegetable culture is needed to ensure that the nutrients benefit profitable crop production and do not become an environmental contamination risk.

Fertilization is an important expense on the farm and its proper management is important to the future success of vegetable production in Florida. Hochmuth, C. K Chandler,J. Cornell, and. Potassium krtigation rrriuirerrn'nts of drip irrigated strawberrv. Albregts, E.

Effect of fertilizer rate on number of malformed strawberry fruit. Clark, G. Andersen, and S. UV-reflective mulch and nitrogen fertility effects on western flower thrips and tomato spotted wilt ,irus in tomato. Hartz, T. Fertility management of dripirrigated vegetables. HmlTechnology J a. Fertilizer ,magenH'lll for drip-irrigated, cgctablcs in Florida. I IortT,xhnology '. Hochmuth, G. Concepts and practices for improving nitrogen management for vegetables.

Hon Technology 2: Nitrogen management practices for vegetable produnion in Florida. Scnice Circ. Brecht, and M. Nitrogen fertilization to maximize carrot vield and quality on a sandy soil. Service Pub!. HS, http:! J Fertilizer lssues ' Smajstrla, A. Irrigation scheduling of dripirrigate lected ,egetables in Florida, EI There arc many attributes for effective media, including the ability to retain moisture and nutrients, ability lo provide good aeration and drainage, availability at an acceptable price, and chemical and physical attributes conducive for plant growth.

In recent years, there has been a trend in which more traditional organic components, such as peat or wood products, have been partly supplanted by an increasing array of waste-product compost products. This paper reviews some important issues in the utilization of urban waste compost products, such as plant response to different percentages of compost in the growing media as well as compost maturity.

Ornamental crop production is one of the m,uor types of horticultural production in Florida. Since in the 19th '. In recent years, the rate of increase has accelerated. There are certain unique attributes to or11ame11tal crop production in addition to its high and rapidly increasing economic value.

The vast majority of ornamental crops are now grown in containers and when the plant is sold, the rooting medium is sold with it. This ne cessitates the regular acquisition of new growing meclium supplies each time a new crop production cyde is begun. Some nurseries mix their own media while others purchase pre-rnixed media. While there is no perfect growing medium for all ornamental crops under all growing conditions, most growers want a grow i 11 g substrate that is consistent, reprodllcible, readily available, easy to work with, cost effective, and with the appropriate physical and chemical properties Poole et al.

U nifrmnity aud consistencv of physical and K.. Ionic11lt11re lkp. Lent er, ,l:! FL 3'l'. Florida Ag-ric. To achieve these criteria, growers and substrate producers combine different types and amounts of organic and inorganic components. Peat is most traditionally nsed as the organic component in horticultural substrates.

Peat is a naturally occurring material formed chiefly from the partial d avoid this problem, manv wood products are composted before they are used as components in growing substrates. Composting is the controlled decomposition of organic matter to a point where the product can be safelv and beneficially used Rodak et al. Other organic materials besides wood products also can and are Table 1.

General recommendations for physical and chemical properties of container growing media for bedding plants, foliage plants, and woody ornamentals Fonteno, ; Warncke and Krauskopf, ; Poole et al. Increasing urbanization throughout the 20th century has created concentrated populations producing large amounts of urban waste products. Plant responses to increasing quantities of compost in the growing media are variable. Some compost products can produce larger plants than control substrates, but to be cost effective for ornamental plant production, compost products only have to be equally effective as the control medium if it is available for a comparable price.

In a study with three subtropical ornamental species, Fitzpatrick did not observe any significant differences in growth of jasmine Jasmine volubile Jacq. However, growth of ligustrum J,igustrum japonicum Thunb. Because of the highly diverse nature of urban waste, the use of urban waste compost as a component in the growing media for ornamental plants can be challenging. For example, Fitzpatrick reported that dwarf schefflera Schefflera arboricola Haya ta and spathiphyllum Spathiphyllum Schott.

However, plants grown in the biosolids compost that had been made from chemically-treated biosolid produced smaller plants than plants grown in the compost made from untreated biosolids. The chemically-treated biosolid compost had substantially higher soluble salt concentrations than the untreated biosolids compost. Both begonia Begonia x semperjlorens-cultorum Hort.

Compost maturity is one of the most important factors to understand before using compost products in the growing substrate. Reasons for the disparity between the compost types included higher soluble salt levels in the municipal solid waste compost and that the municipal solid waste compost was less mature with a C:N of 29 compared to a C:N of 17 for the biosolids compost.

Example of bioassay using radish seeds. The flat filled with the control medium is on the left while the flat filled with the compost in question 4-wk-old municipal solid waste compost is on the right. It is difficult to define one set of recommendations that apply for all compost use in container production. The appropriate amount of compost to use in container media will vary with the type of plant being grown as well as with the compost product.

Furthermore, it is difficult to recommend one compost product over another. Growers should look for compost products that will meet the physical and chemical parameters for the crop that they are growing. In general, compost products suitable for container use should be to inch mm particle size and should have a pH of 5. The nursery industry's impact on Florida's economy.

Ornamental Outlook 8 2. Dickey, R. Conover, and J. Container growing of woody ornamental nursery plants in Fl01 ida. Fitzpatrick, G. Compost utilization in ornamental and nurs ery crop production systems. In Stofella and Kahn ed. Compost utilization in horticultural crop systems. Sludge processing effects on compost quality. BioCycle 27 9 Evaluation of potting mixes derived from urban waste products. Fonteno, W. Reed ed. Water, media, and nutrition of greenhouse crops. Ball Pub. Batavia, IL.

Jimenez, E. Evaluation of city refuse compost maturity: a review. Wastes Klock-Moore, K. Bedding plant growth in greenhouse waste and biosolid compost. HortTechnology 9 2 Klock, K. Growth of Impatiens 'Accent Red' in three compost products. Compost Sci. Leege, P. Thompson ed. Test methods for the examination of composting and compost, 1st ed. The C. Composting Council, Bethesda, MD. National Bark and Soil Producers Association. Uniform nomenclature for quality soil products.

Available at www. Nelson, P. Root substrate. In Greenhouse operation and management 5th ed. Obeng, L. The cocomposting of domestic solid and human wastes. World Bank Tech. Poole, R. Conover, and. Soils and potting mixtures. Joiner ed. Foliage plant production. Olds, M. Goldman, M. Franz, and]. The complete book of composting. Rodale Books, Emmaus, PA. Rynk, R. Willson, M. Singley, T. Kolega, F. Gouin, L.

Kay, D. Murphv, H. Hoitink, and W. On-farm composting handbook. Ithaca, NY Warncke, D. Greenhouse growth me dia: Testing and nutrition guidelines. Michigan State Cniv. Facts Ext. East Lansing. Whitcomb, C. Growth media. In Plant production in containers.

Lacebark Pub. Stoffella, and H. Soil organic amendments are usually in the form of animal manures, green manures cover crops , and composts. Composts, derived from various organic wastes, have become increasingly popular soil organic amendments. Research has demonstrated that compost can serve as a soil amendment to increase organic matter, improve microbial activities in soil, provide nutrients, and ultimately improve plant growth and yield. However, composts are produced from various organic wastes and consequently, environmental concerns are always an issue in compost utilization.

The potential often exists for heavy metals to accumulate in the soil and sometimes in the edible parts of vegetable plants. Excessive nutrients or metals released from composts may be leached out of the root zone and into groundwater by irrigation or by rainfall. Vegetable crops are grown mostlv on sandv or gravelly soils with a small but significant J;ortion on ,His tosols organic soils.

These soils, excluding Histosols. Using organic materials as soil amendments on Florida soils usuallv improves soil fertility and generally, but not always increases crop vields. Indeed, animal manures supplv significant quantities of' essential pla11t nutrients and increase soil organic matter Hochmuth t't al. Cover crops are used to improve soil physical properties, increase soil organic carbon, conserve soil water, reduce surface runoff, and recycle nutrients during the heavy summer rains Hubbell and Sartain, l S 80; Reeves, ; Mansoer et al.

Sunn hemp Cmtrilaria juncea L. Li and H. Bryan, Tropical Res. Center, liniv. Stoflella, Indian River Res. Center, Univ. Pierce, FL , Contribution published in Soil Crnp Sci. A series or co, er crop projects an--cnrrently in progrt'ss in south Florida. Composts have been increasing in popularity as soil orga1:ic amendments. Compost application to commercial vegetable crops is relatively new in Florida. In this paper we briefly review the horticultural and c11,irnnmental effects of compost utiliz,1-tion in commercial vegetable crop production systems in Florida.

Mineralization of a compost depends on the compost's composition, ma turity, and the soil conditions moisture, temperature, etc. Elemental composition of three typical composts used for vegetable production in south Florida Zhao et al.

Mg, and P increased, whereas extractable K was not affected. Similar Ii ndings were also reponed b, Clark et al. Hoffmann reported that repeated applications of MSW compost over a long-term increased soil organic C from 20 to 62 g kg-'. The amendment of soil with compost increases humus formation. Humic acid is a major extractable component of soil humic substances; FA is usually a minor component of soil: and soil humin is a major nonextractable component Stott and Martin, Bovd and Sommers reported that soils amended with sewage sludge had 5 and?

Glucosidases or glycoside hydrolases are en' zymes that catalvze the hydrolysis of various glycosides. Indeed, the hydrolysis products of 0-glucosidase arc helie,ed to be important energy sources for microorganisms in soils Tate, 19 5. Zhao et al. Dehydrogenase, urease, pyrophosphatase, and 0-glucosidase activities were positively affected by addition of these three composts to soils.

The cocompost treatment signihcantlv increased all enzvnw activities except pyropl10sphatase. En zyme activities, except that of pvrophosphatase, were the lowest in plots treated with inorganic fertilizer. The levels of dchydrogenase, urease, and pvrophosphatase activities resulting from addition of organic residues began to decline about 30 d after application of soil amendments. Bv contrast, 0-glucosidase in co-compost amended soil remained 5 Lo 7 times higher throughout the entire d experimental period than in other treatments in which organic matt.

No similarly effective soil fumigant is commercially available. Hoitink et al. The high level of microbial activity in the biomass is attributed Lo the general soil microflura. It is believed to pren:nt the germination of the spores of pathogens and thereby avert infection of the host. Such disease suppression properties are dependent on compost composition and maturity, organisms to be suppressed, and environmental conditions. Composts have been evaluated for their capacities to suppress nematodes and plant pathogens in Florida.

Composts have had inconsistent effects on nematodes and plant pathogens affecting field or greenho11se grown vegetable crops Table 2. Bryan et al. However, using similar composts, Mannion et al. Thcv reported no ef fects of compost amendments on plant-parasitic nematode populations during a 2 yr experiment. Ritzinger et al. Ozores-Hampton ct al. In most experiments. Responses of vegetable growth are significantly affected by compost composition, maturitv, and soil conditions.

For example, effects of composts on tomato yield are presented in Table 3. Obrcza ancl Reeder also suggested that the lower yields of to mato from compost amended plots in their experiment had been caused by incorporating immatun compost. Therefore, responses of crop to compost amendments is largely depended on compost quality.

Clearly, reliable methods to determine compost maturity and stability and pathogen suppressivity should be developt'd. Of parlicular concern is the possi-Table 2. Effects of compost amendment on the incidence of nematodes and bacterial wilts of vegetables grown in Florida. Yield responses of tomato to compost amendments from experiments conducted in Florida. Excess nutrients or metals released from composts may be leached from the root zone by irrigation or rainfall Li et al.

During to , Zinati ct al. One of three composts used in the experiment significantly increased concentrations of Ni and Pb in amended soils. They reported no significant changes in concentrat. Nutrient leaching rates in Florida from sugarcane filtercake, biosolids, and three mixtures of MSW, and biosolids applied to the surface or a Florida fine sa11dy soil have been evaluated Li et al.

After leaching with water equivak11t to '. The concentrations of N However, the U. Clearly, leaching of nutrients in relation to the drinking water standard must be considered in selecting compost application rates and frequencies, particularly on soils nilnerable to nutrient leaching. High variability in the quality of operations between and within compost production facilities leads to unpredictable compost quality. Often immature composts display plant phytotoxicity. Composts derived from organic wastes are Lhe most available soil organic amendment, and technology has been improving compost quality and quantity signifi cantly.

Sewage sludge compost's cumulative effects crnp growth and soil prnperties. Utilization 1 :'. Bmd, S. Hrnnic and f'ulvic acid fr"ctiom from sewage sludge. Humic substances in soil and crop scicnns. Madison, WI. Brown, R. Stone, and V. A procedure was developed which was acceptable to the scientists and still provided tome information on where the most likely outcome would fall. The procedure followed was to enter the mid-point of the range in the table; for example, if the range were 0 percent to 15 percent the mid-point would be 7.

Upon entering the value for the mid-point, the participant was asked to indicate whether the percentage of lakes no longer able to sustain fish populations would be likely to lie above or below the mid-point. In our example, at pH value of 6. Once the participant decided whether the impacts were1 likely to be above or below the midpoint of the range, an "X" was placed either above or below the mid-point in order to express this weighting of the probabilities see Table b.

The elicitation continued until estimates for ail the pH levels were developed. In many cases the participant felt that the incremental change of. S pH5. At that pH, the concen- tration of inorganic monomeric aluminum was estimated to be approximately. In some cases, the participants were so uncertain that they were unable to weight either the "high" or "low" interval. In such a case, no weighting was placed on either side of the midpoint.

Not all of the elicitations began at the highest pH values, 6. In a number of elicitations, participants elected to begin at pH values around 5. This is not sur- prising, because the majority of bioassay experiments, as well as anecdotal literature, note effects at a pH of 5.

The investigators do not believe that this change in the procedure affected the estimated ranges. Review and. Assessment of the Elicited Damage Functions The final step in the eiicitation interview consisted in a review of the range and weight which resulted from the eiicitation. During the review, the participant and the investi- gator examined the range of impacts listed at the different pH values.

If the participant believed that the estimates accurately represented his beliefs, no changes were made. On the other hand, if there were distributions which seemed inappropriate, then these were reconsidered and changed where appropriate.

Often this amounted to the alteration. Following these revisions to the estimates, if sufficient time was available, the interview was closed with a brief discussion concerning the participant's evaluation of the approach and his confidence in the use of its results.

Table fc-6 presents the results of each elicita- tion. The data will be interpreted in Chapters 5 and 6. Section 5. There are a number of ways to interpret and use the estimates obtained from the elicita- tion. One way is to simply show the range of estimated effects. Since each expert esti- mated lower and upper bounds of effects, these can be used to dimension the range of effects due to a change in pH.

If two additional assumptions are made, probabilistic estimates of damages from acid deposition can also be obtained. It is important to recognize that both the use of a 95 percent confidence interval and a weighting are assumptions. There is no quantative or stat- istical justification for either assumption. However, a 95 percent confidence interval was felt to be reasonable since during the elicitation the scientists were asked to dimen- sion a range of potential effects so that, in their opinion, the actual impact would almost certainly lie within that range.

Assuming that the range represents a high confidence interval is consistent with the way the elicitation was conducted. The assumption of a weighting is more problematic since the scientists were not asked during the elicita- tion to determine what the relative probabilities were between the weighted and un- weighted segments.

Whenever the scientists were asked to actually assign different probabilities to the different segments, they resisted making the estimate. It was felt that the simple weighting used in the elicitation pushed the limits of the scientists ability to dimension the uncertainty surrounding the effects estimates. The scientists simply did not feel that they could provide reliable estimates of actual probabilities, but they felt they could indicate on which side of the range mid-point the actual outcome would most likely fall.

Given that this was all the information that could be reliably obtained, the task facing the project investigators was to design a method that credibly used this sparse data. Since the specification of a confidence interval and interpretation of the weighting are both assumptions, it is important to perform a sensitivity analysis around any selected values.

Confidence intervals of 90 percent anld 80 percent were used along with a 95 per- cent confidence interval to test the sensitivity of the confidence interval assumption. In addition to the weighting assumption, sensitivity analysis was performed using a and 5A weighting. These different confidence intervals and weighting assumptions were felt to bound the reasonable range of assumptions. The 95 percent confidence interval is quite a high con- fidence interval ie. Conversely, the 80 percent confidence interval was felt to be a lower bound.

The results of the sensitivity analysis are shown in more detail in Appendix A; however, it was found that the assumed confidence interval had a significant effect on the damage estimates, but the assumed interpretation of the weighting had a minor impact. This is an important finding since the interpretation of the weighting is the most uncertain assumption. Further, this result justified the emphasis placed on obtaining accurate esti- mates of the potential range of effects while settling for a simple weighting scheme to indicate where within this range the most likely outcome might fall.

Example 1 Assume that for fish species X and a pH of 6. Assuming a 90 percent confidence interval and a weighting results in the cumulative distribution shown in Figure Example 2 Assume that for fish species X and a pH of 5. Given this cumulative probability distribution, the fol- lowing holds true: 30 equals. A weighting results in probabilities of. Recall that the estimate of the number of lakes damaged was found, in this application to be relatively insensitive to the weighting interpretation.

This section will outline the steps in the estimation of damages from acid deposition based on the elicitations. A simple illustration of these steps and a presentation of results from a test case sensitivity analysis of the confidence interval and weighting assumptions can be found in Appendix A. Table 5. Step One is the calculation of aggregate cumulative probability distributions of damages for each species of fish at each pH level. For example, five elicitations were conducted for self sustaining populations of brook trout.

The five different self sustaining brook trout elicita- tions were combined to form aggregate cumulative probability distributions of damages at each pH by first calculating cumulative probability distributions for each scientist's elicitation and then averaging the distributions. A computer program using simple numeric techniques was constructed to perform these computations. Step Two involves determining the present distribution of pH levels across Adirondack lakes.

This data base and others used are described in Section 5. Step Three is the presentation of a hypothetical case used to derive the change in the distribution of pH values caused by increases or decreases in acid loading. Step Four is the calculation of the incremental damages from the shift in the distribution of pH values calculated in Step Three. This is a conditional probability calculation. It is the probability of incremental damages given the current distribution of fish habitat in the Adirondacks.

Step 2: Obtain current distribution of pH values for Adirondack lakes. Step 3: Derive the change in the distribution of pH values across Adirondack lakes caused by increases in acid loading. Output: Given a predicted change in the distribution of pH values across Adirondack lakes, a cumulative probability function of the incremental number of lakes expected to be damaged. To calculate this combined distribution, the distributions of damages to lakes segmented by pH class must be convoluted i.

Referring back to Figure , the figure shows the probability distribution of damages if or a fish species in lakes with a pH of 6. A similar distribution could be graphed for lakes with a pH of 6. The assumption of perfect correlation between these two distributions would mean that if actual damages at a pH of 6.

In terms of the cumulative probability distributions, this means that if the actual damage outcome turns out to be that outcome associated with a. The assumption of perfect independence implies that finding high levels of actual damages in lakes with one pH does not change the probability of high or low damages in lakes at neighboring pH values. Instead of assuming perfect correlation or perfect independence, a compromise assump- tion of partial correlation between distributions is possible.

With partial correlation, a high damage outcome at one pH level does not imply a high damage outcome at a neigh- boring pH level, but it does imply that the probability of high damages at the neighboring pH levels increases. The assumption of perfect correlation results in the most uncertainy i. This stems from the fact that, with perfect correlation, if damages at one pH turn out to be very high, the damages at neighboring pH levels will also be very high.

Thus, extreme values are always coincident. This tends to increase the probability that actual outcomes will fail in the tails of the joint distribution. However, it does not change the upper and lower bounds of the distribution. Thus, the assumptions of perfect correlation and perfect independence can be used to bound the uncertainty. The appropriate dependence assumption was discussed with scientists during the pretest phase of the project. The scientists indicated it reasonable to assume that if actual damages at one pH level were in the low part of the distribution, then actual damages at neighboring pH levels will also be in the low portion of their distributions.

This implies that underlying factors which make estimates of damages uncertain are correlated across pH levels, and that if scientists learned that actual damages caused by pH 5. For this study, perfect correlation was assumed. This assumption provides an upper bound to the uncertainty in the estimates and it is mathematically much easier to work with than partial correlation.

By assuming perfect correlation, it is possible to sum calculated distributions of damages across different "clusters" of lakes to obtain total distributions of damage to lakes. A "cluster" of lakes is a set of lakes that have the same current pH level and the same ending pH level after the shift in pH levels. Appendix A presents a simple example of these calculations and the results of a "Test Case" sensitivity analysis of the weighting and confidence interval assumptions.

This is incorrect. The assumption of perfect correlation implies nothing about the placing of weights during the elicitation. The scientist place the weights in the manner they feel most appropriate. Assumptions of correlation or independence influence how the resulting distributions are combined. Published and unpublished data provided by a number of othelr investigators were also used. These in- cluded data collected in by Dr. Carl Schofield unpublished data ; a characterization of Adirondack lakes provided by Dr.

This section will describe salient charac- teristics of the DEC data as it was represented on the Adirondack Waters Management System Tape, as well as the manner in which the data were interpreted and used in a regional assessment of fish damages.

To sort the data into meaningful units for analysis, the variables in Table were reorganized into a working data base. The data base is not entirely com- prehensive, as not every ponded water has a complete record. For example, while there are a total of pH records within the data base, only of these are contained within the Chem-Current File the file containing most current chemistry survey data for those waters which possess chemistry surveys.

Similarly, while there are a total of alkalinity records for Adirondack ponds, only are contained within the Chem- Current File. The pH measurements were obtained with a'pH meter under air-CO2 equilibrium condi- tions. In the initially published results, 25 percent of the surveyed waters registered pH readings below 5. There were a total of 'records for calcium and for magnesium within the Data Base. Record type 2. Watershed 3. Date Recorded Date of Samples Depth ft.

Measurement Method Remarks W. Source Sample Type 2. In order to compare current levels of acidification with these historical records, the investigators recorded the current pH values using both a pH meter and a Hellige comparitor. In reporting the results, Pfeiffer and Festa showed that the colorimetric Heilige comparitor readings were consistently higher than the pH meter determinations see Figure However, when Schofield compared colorimetric measurements to meter pH measurements, he concluded that the agreement between the two methods was much closer than stated by Pfeiffer and Festa.

Schofield concluded that the pH meter determinations reported in Pfeiffer and Festa were between. Hence, the pH deter- minations for the ponded waters sampled in are probably between. The investigators have been unable to determine what percentage of pH listings recorded by the DEC and listed in the data base are in error.

In order to assess the potential bias in data base pH records, a regression developed by Schofield relating pH to pCa was used by the investigators to determine the pH of the Adirondack waters for which both pH and calcium data were available.

The mean listed pH value for the sample was 6. The standard deviation of the pH values was. While the difference between the two values is important, the investigators didn't believe it to be large enough to justify not using the pH records contained within the data base. The seasonal variability of the pH within individual lakes caused by biologic production, snowmelt, and in some cases, fall rainstorms, is probably equal to or greater than the variation expressed in the calculation of the lake pH values.

Figure demonstrates the considerable variation in the pH of one Adirondack lake's summer-ice free-surface pH values. Readers, however, should be aware of this systematic bias in the characterization of pH values in the data base used in this analysis. It possesses a well-defined inlet and outlet. All of the fish species for which damage elicitations were performed are included the Data Base.

A data sort was per- formed to establish an inventory of Adirondack lakes posessing both chemistry records and presence-absence data for fish populations. Figure illustrates the sort pro- cedure. Of these, possessed fish records,. Records dated from to the present were considered current or indicative of the present pH and fish population status.

Of the examined, were surveyed prior to Assuming some change in the pH of those 2SO lakes between and the present indicates that our data probably over- estimates current pH and fish populations status within the region. There has been no published estimate of the rate of acidification in the Adirondack Region between and the present, but W.

Watt et al. In searching the files for a pH record, the algorithm also looked for calcium and alkalinity records. Of the lakes with pH records, there were which did not possess alkalinity records. Step 2 calculated the pH range of the ponded water's pH value. Lakes were assigned one out of 42 possible pH ranges. Increments of ,1 pH between 8. If there was no record, or if the elevation was blank, the elevation class was set equal to "unknown". High elevation lakes in the Adirondack Mountain Region have been noted to possess both depressed pH values and reduced fish populations Pfeiffer and Festa, ; Schofield, b, , In a survey of lakes above feet, Dr.

In , an additional 35 lakes were surveyed. Is there an elevation record later than ? If so, calculate elevation class. If not, or if elevation is blank, set evaluation equal to "unknown". Is there an alkalinity record later than ? If so, calcualte alkalinity class. If not, or if alkalinity is blank ,set alkalinity class to "unknown". Is there at least one fish species record later than ? YES Read all job species records with the same data as the most recent one and set flags for each of the six species being looked for.

Add 1 to total for each fish species found broken down by alkalinity, pH range, and elevation class. Add 1 to total for all fish species broken down by alkalinity, pH range, and elevation class. Add 1 to total for all takes broken down by alkalinity, pH range, and eleva- tion class. Fish surveys conducted at the same time indicated that 82 percent of these acidic, high elevation lakes are devoid of fish.

If there was no alkalinity record, the alkalinity record for that lake was set equal to unknown. After assigning the lake to a pH, elevation, and alkalinity category, the program recorded which, if any, of the 6 species of fish for which elicitations were performed were present within the lake either in or later. A summary of this data, not includ- ing elevation and alkalinity records, is shown in Table Table contains a summary of the data excluding pH categories for the Adirondack Mountain Region.

There were no records of brook trout lakes below pH 4. Of the 2, lakes which comprise the Adirondack Ecological Zone, only , or 34 percent, have been entered into the data base. According to the DEC unpublished data , the average size of the ponded waters in the Adirondack Ecological Zone is The DEC cal- culated the remaining unsurveyed ponds to have an average size of approximately The majority of these smaller ponds are found at high elevation sites on generally more sensitive soils, and, consequently, can be expected to have, on average, lower pH values than those ponded waters contained within the sample constructed for this analysis.

ERC implemented a separate sort algorithm in order to differentiate between those waters containing stocked and naturally reproducing populations of brook trout and lake trout. The results of that sort indicated that there were a total of 77 lakes with stocking records and recorded brook trout populations after Of these, he records that approximately ponds, representing some 12, acres, receive annual stocking with fall fingerling wild x domestic hybrids.

Pfeiffer predicts that "about 25 percent of the existing viable acreage will succumb to acidifiction by However, in a recent personal communication, Pfeiffer indicated that there had been a slight improvement in the condition of brook trout ponds since the beginning of monitoring in He indicated that, while the pH of ponded waters in central and western New York had declined over the period, that the pH had increased slightly in eastern and southern New York.

Pfeiffer lists ponds within the Adirondack Ecological Zone as being stocked with brook trout. The DEC confirmed that at present, many stocking records have not been entered on the data! Damages to stocked and unstocked habitats were estimated. The Data Base was further analyzed into the six drainage bases which jointly constitute the Adirondack Region. The results of this sort are represented in Table Elevations apparently strongly influences alkalinity. This compares with 1 percent of the lakes above feet.

Table represents the same terrain, according to the calcium level of Adirondack lakes analyzed by elevation and major drainage basin. While direct comparison between i Tables and is difficult, the general trend of increasing alkalinity values and cal- cium values with decreasing elevation is evident in both. There are an additional 33 private lake trout waters, which Pfeiffer assumes have self-! NO K The base additions can be taken to represent either reductions in the input of acidic deposition; or, presuming no change in the level of acidification, a mitigation strategy of base addi- tion.

It asumes that all Adirondack lakes have the chemistry outlined above, provides no time rate of change for the aquatic chemistry, and makes no attempt to relate the change in aquatic chemistry to changes in the rates or concentrations of acidic deposition. In order to calculate the change in pH, two computer runs were executed. The first fixed or esta- blished the pH at values from 4 to 8 in 0. The model then calculated the amount of acid or base required to shift and fix the pH values at a new steady state.

The model calculated the extent of change in the pH of lakes relative to the fixed pH values along the bottom axis of the graph. The results of the runs are shown in Figure Changes in lake pH represented in Table were calculated using Figure Notice that the buffer intensity of the system seems weakest in the pH values ranging from approximately pH 7 to pH 6. Lakes below 4. At pH 4,5 and below, the model results were highly variable due to the in- creased aluminum buffering in the system.

However, lakes with pH records equal to or below 4. He attributed this to the hypothesis that, for Adirondack waters, this was the region of minimal buffering intensity. The model runs depicted in Figure indicate, however, that there is less buffer intensity between pH 7 and pH 6. The model runs indicate that the Adirondack lakes are strongly buffered by the aluminum system rather than the carbonate system. In a carbonate buffered system, the maximum buffering intensity would occur at pH 6.

As discussed pre- viously, while the aluminum buffering systeijn prevents or slows down further lake water acidification, it tends to stabilize the systjem at very toxic conditions due to the re- sultant combinations of pH and aluminum levels. There are 10 records of fish populations in water with pH less than 4. Ninety percent of those low pH lakes contained brook trout, one contained white suckers. For example, for a lake with a pH of 6.

The lake would shift from a pH of 6. Results for brook trout and lake trout are expressed both for stocked and self-sustaining populations. The computations of incremental damage were made using the following assumed parameters: 1.

Three of the four lake pH shifts calculated using the model described in Section 5. The second section presents the results of a base addition scenario which would result in the increase in pH of the cluster of lakes. A slightly different procedure was used to examine the effects of base additions to the lakes. The third section presents a comparison of the response of the different fish species habitats and an evaluation of the results using two different cal- culation procedures.

Both of these scenarios represent rather large increases in acid deposition. Based upon this estimate, the two scenarios represent roughly a 50 percent and a percent increase over present levels of acidification from antropogenic sources. The damages range from a lower bound of 4,7 lakes, or approximately 1. The median value is Because the results represent a cumulative probability distribution, the median represents the number of lakes which divides the range of probabilities of damages into two equally likely seg- ments.

The expected value of damage is the mean of the probability distribution. If the mean, as in this case, is less than the median value, the marginal probability distribution representing the shift would be skewed towards the lower end of the probability range. Conversely, if the mean is greater than the median, the expected changes in the marginal distribution would be skewed towards the upper half of the range. The results expressed in column one indicate that there is a 10 percent chance that damages occurring to the sample of brook trout lakes would be equal td or less than S Jakes.

Another way to use the information contained in the cumulative probability distribution is to calculate the probability that damages,from the shift in distribution of pHs across Adirondack lakes exceed a given level. Since the cumulative probability indicates the likelihood that damages are equal to or less than a given level, one minus the cumulative probability will equal the likelihood that damages exceed a given level.

Using this interpretation, the following hold: o probability that the number of lakes damaged will exceed one quarter of the lakes i. Column two represents the same calculation with a 90 percent rather than an 80 percent confidence interval. As expected, the range has narrowed somewhat, especially at the lower probability levels.

The change in the expected value shifted from This represents a change of. The change in the median value is equal to. Column three is calculated with an 80 percent confidence interval and column four with a 90 percent interval. As can be seen the expected value of damage in both columns three and four is greater than half the expected value of damages in columns one and two. This result was expected based upon the aquatic chemistry model output shown in Figure The change in the pH level of the "typical" Adirondack lakes is not linear with respect to changes in the amount of acid or base added to the system.

Table compares the means, or expected values, for shifts occurring to stocked and unstocked populations of brook trout given different acid additions. An examination of the lower bounds and upper bounds from the elicitation for self-sustaining brook trout populations at pH 4. Average lower and upper bounds for the stocked populations were The stocked population at pH 4.

The average lower bound was The average upper and lower bounds for the self- sustaining population at 4. These results are similar to those found in the laboratory analyses conducted by Baker and Schofield Baker, In that study, Dr. Baker determined that in order to prevent measurable reductions in the survival of early life history stages of brook trout, the pH of the typical Adirondack surface water should be greater than or equal to 4.

This implies that as the pH declines, the difference in sensitivity between stocked and unstocked lakes declined. At some pH levels, all fish are affected. Table presents the expected values for changes occurring to the remaining five species of fish considered during the project. Damage calculations were then performed on the entire set of lakes for which the investigators possessed both chemistry and any population data concerning brook trout and lake trout.

Fat head minnow results were not included because of the small size of the sample contained within1 the DEC files. Our results do not necessarily contra- dict those studies, but can be explained by the distribution of white sucker lake habitat compared with brook trout habitat recorded in the DEC data base. Twenty-seven per- cent of the lakes possessing records of white sucker have a pH greater than 7.

Similarly, 46 percent of the lakes with white sucker have pH records where 6. Only 43 percent of the brook trout lakes have intial pH values equal to or greater than pH 6. While 73 percent of the white sucker lakes won't shift below 5.

Caution must be used in interpreting the results listed above. They are not simply rela- tions of sensitivity of different fish species to acidification. The results listed in Table and Tables through should not be interpreted as representing the sensitivity of different fish species to pH stress as expressed by the scientific partici- pants within the study. These results are a sample application of the data developed in the elicitation interviews, and are based upon additional inventory data and water chemistry modeling information.

A new algorithm was required to predict the effects of a base addition to Adirondack waters. The algorithm developed for predicting incremental damages, which has been previously described, could not be used to calculate decremental changes in acidification. First, the number of lakes which could support fish, in our case, self-sustaining brook trout populations in a natural, pre-acidified condition, was estimated.

Only populations of self-sustaining brook trout were evaluated in this scenario. To evaluate the effects of varying levels of acidification, it was necessary to make an assumption concerning the ability of lakes in this baseline chemical condition to support fish populations. It was assumed that 80 percent of the lakes with pH values between 7. Table reports the results of this work. Where the estimated damages were very high, this caused division by a very small number and this, in turn, caused unacceptable imprecision in the results.

If, alternatively, the damages were estimated as It is known that these waters can sustain brook trout populations at or below pH 5. For the 90 percent confidence level, there is assumed to be a 10 percent probability that the true value lies outside the range given. The result is that when base additions are considered, the upper end of the distribution will be very sensitive to the elicitation results and the assumed confidence interval.

To adequately handle scenarios where there are base additions, changes should be made in tine numeric algorithm that calculates incremental change. For acid additions, the cur- rent algorithm for the calculations of damaged lakes is appropriate. The results were calculated assuming a baseline distribution of Adirondack lakes between pH values of 7. Using the pH shift presented in Figure , the number of lakes which were contained within the range between pH 5.

Such an addi- tion is equivalent to a return to the present level of acidification from the predicted baseline. The results shown on Table indicate that brook trout habitat could be expected to increase from a lower bound of 3. The expected value of the change is equal to 16 percent, or 69 out of lakes. Alternative Damage Calculation In order to further evaluate the validity of the damage estimates generated using the elicitation results, an alternative method of calculating damages was used for "self- sustaining" brook trout lakes in the Adirondacks, This method involved utilization of the "baseline" pH distribution assumed to represent the chemical condition of the lakes prior to anthropogenic acidification discussed in 5.

Damage estimates were calculated by considering changes from this calculated Baseline" pH distribution to new pH distribu- tions reflecting varying levels of acidification. In order to evaluate the effects of vary- ing levels of acidification, it was necessary to make the same assumption concerning the ability of lakes in this baseline condition tp support fish populations; see Section 5.

A summary of these additions is shown in Table The results of the third shift, from the assumed baseline to the present state, are par- ticularly interesting, since it can be used to provide some information on the accuracy of the eiicitations and algorithms. Of course, the elicitations were designed to estimate the effects of pH on fish populations.

If other factors are causing damages to fish popula- tions, then these figures would not necessarily correspond. The present number of Adirondack lakes listed on the data base which are capable of maintaining self-sustaining brook trout populations is Using the incremental damages generated by the elicitation results and the assumption that 80 percent of the lakes between 5.

It is assumed that 80 percent of the lakes between 5. JLJL lakes are the number of observed lakes which contain brook trout populations on the data base between a pH of 5. In accomplishing this, two different sets of results were developed.

The first set of results, which is shown in Table , represents the results of the elicitation interviews with participating scientists. The second set of results, which are based on the elicitation results, are contained and discussed in Chapter 5.

The results in Chapter 5 provide an example of how the data generated in the elicitation interviews can be applied. Because they are based upon inventory data that is expected to be significantly improved prior to , and because the uncertainty surrounding this data wasn't, specifically dimensioned, the conclusions to be drawn from these results should pertain to the adequacy of the procedure, instead of the specific numeric dimen- sioning of the effects of acidification on Adirondack fish populations.

The framework was designed to interpret the scientific uncertainty in estimates of the relationship between acidification and aquatic effects and to further assist in extrapo- lating spatially limited scientific data to regional areas.

If successful, it will augment scientific research by reframing effects information so that non-scientists can better evaluate the probability of different levels of regional environmental damage. The framework does not, however, replace effects research, as it does not generate new hypotheses or data.

It simply organizes existing data and interpretation into a format complementary to conventionally presented scientific results. To evaluate whether the framework accomplishes its primary goal, two questions need to be answered: 1.

Are the analytic procedures and the results of the framework credible to the scientific community? Are the results of the framework helpful to economists, policy analysts, and decision makers? A framework designed to interpret scientific data and knowledge must have scientific credibility and endorsement if it is to be a useful too! The framework developed and applied within this project has not received general or widespread scientific comment. As a result, the credibility of the approach is generally untested.

The project has, however, been reviewed by a number of the participating scientists and a review panel at the National Acid Precipi- tation Program Effects Research Review Meeting. A recognized advantage of the framework is that members of the scientific community directly extrapolate from and interpret the results of their investigations, rather than having less scientifically knowledgeable policy analysts performing this extrapolation.

Given the considerable uncertainty surrounding the performance of regional damage estimates, which depend upon uncertain damage- relations and inventory data, it seems unlikely that any framework addressing this problem will receive unequivocal scientific endorsement. The second question concerns whether the outputs of the procedure will be useful as inputs to policy analysis and economic benefits studies.

Here a more definitive answer is available. The type of information produced by this project is required by all policy assessment frameworks, and is also necessary for economic benefits studies. Policy analysis cannot be performed without a regional characterization of the resources at risk and the likelihood of different levels of damage on a regional level. To know that effects have occured at dispersed sites, mainly in the northeastern U. By dimensioning the uncertainty for the aquatic and the other acid deposition caused effects many important policy questions can be addressed.

In particular, any policy assessment based on uncertain information must have the uncertainty in the parameters dimensioned if responsible decisions are to be made. In the past, ad hoc procedures for incorporating uncertainty into assessments have been used by policy analysts.

Procedures directly utilizing scientific expertise can signi- ficantly improve this aspect of policy evaluation. In addition, it would allow analysts to determine the value of additional scientific research and whether reductions in acid deposition should be sought while additional effects research is being performed.

February , Esti- mates of damage to fish populations were made directly by scientists participating in the research. These effects estimates are not directly available from published scientific experiments since most of these experiments are performed in the laboratory and cannot easily be extrapolated to natural habitats or, where research results are available for fish damages in natural habitats, few sites have been studied.

The implications of the current scientific research for estimating the effects of acid deposition on fish populations are not straightforward and require the considered judgment of the scientists performing the research. Since point estimates would be unreasonably precise given the current uncer- tainties, the elicitation focused on estimating the expected range of potential effects for a given pH value. The estimates developed in this project have the advantage of being expressed quanti- tatively.

As such, they can be easily reviewed and, if need be, revised in the light of new scientific information. For example, the damage relationships specified in this project estimate effects as a function of pH, aluminum, and calcium concentrations. If new research determines that some other variable is important to the prediction of effects, then that variable can be incorporated. Similarly, scientists can easily revise the esti- mates of effects either upwards or downwards as new information becomes available from completed projects.

Another accomplishment of the elicitations used in this project is that the damage rela- tions which resulted from the application of the framework integrate many different mechanisms and possible causal agents of fish population decline, e. This characteristic of the damage relation allows for a relatively simple and understandable dimensioning of the predicted effect and its uncertainty which will be easily understood by policy analysts.

This allows for the explicit representation of current scientific opinions and the development of a regional perspective for acid depo- sition effects. The probabilistic structure of the project and its reliance upon explicitly represented expert judgement in the development of regional effects estimates does, however, generate considerable scientific skepticism.

In this project, scientists were required to perform an assessment role in addition to their responsibilites as effect? Consequently, some con- fusion exists concerning the status of the project, i. The obvious answer is no.

Recall that it is an assessment device useful for i organizing technical information. Its outputs represent the considered judgement of the scientific community. The rationale for the framework assumes that: o Data sets containing statistically valid samples of observations on effects will not be available prior tb , and in some cases the assessments.

This is most likely to come from the scientists performing the actual research. First, projects of this type require an iterative process with extensive interaction between scientists and the project investigators. Both the variables to be explicitly considered in the elicitation and the structure of the elicitation should be determined in conjunction with participating scientists.

This helps to assure that the judgements being elicited can, in fact, be reasonably evaluated by the scientists. One example of the importance of interactive communication between the project inves- tigators and the participating scientists is the specification of variables for use in the elicitation. The determination of the appropriate variables for use in policy assessment can become as complex as it is important. For example, the independent and dependent variables of the damage relations were changed several times during the project as a result of communication between the investigators and participating scientists.

The process was iterative, with each succeeding set of variables being more appropriate to the assessment than their predecessors. While the project investigators suggested the original variables for the analysis, subsequent specifications were the products of discussions with scientific participants. The linkage between the information needs of the policy analyst and the scientific investigator is not straightforward.

Policy analysts are not able to adequately specify information needs to the effects scientists without considerable and extended dialogue. As scientific informa- tion and estimation improves, policy analysts will attempt to incorporate that informa- tion within their assessments. A second conclusion is that, when dimensioning the uncertainty in effects estimates, it is important to try to achieve only that degree of resolution which is scientifically credible or responsible.

Scientific judgements regarding the uncertainty of different acid deposi- tion effects estimates are imprecise. This makes it difficult for scientists to provide judgemental estimates of a precise probability distribution for effects outcomes. If the approach for dimensioning uncertainty requires a level of precision that the scientist cannot achieve, then the scientist will not view the resulting estimates as being credible. The elicitation used in this project explicitly recognizes the difficulty in mak- ing meaningful point estimates for the probability of different levels of effects.

Instead of point estimates, the elicitation estimated the range of potential effects i. The lack of information on causal mechanisms associated with acid deposition effects and the extreme variability in different eco- system's response to acid deposition warrants conservative expectations regarding the precision with which scientists can estimate the probability of different effects out- comes.

A third conclusion is that inventory data concerning resources at risk may be the limiting factor in the performance of assessments concerning acidification effects upon fish populations. While there is considerable uncertainty concerning the effects of acidifica- tion upon fish populations, there may be even more uncertainty in the current status of regional fish populations and aquatic chemistry inventories.

This project focused on dimensioning the uncertainty in estimates of damages to lakes presently containing fish. However, no attempt was made to dimension the uncertainty in estimates of the number of lakes that currently support fish populations. If explored, it seems possible that the uncertainty in the dose-response relationship for certain species of fish. Techniques similar to the approach employed in this project could be useful in dimensioning the uncertainty in estimates of resources at risk.

Interpretation of the project results should be guided by the following remarks. First, the project was designed to evaluate the utility of a particular device for incorporating scientific knowledge and advice within policy debates. As such, the damage estimates generated should be viewed as preliminary. Furthermore, the proper emphasis of the report should be the results listed in Chapter 4, which are the outcomes of the different elicitation interviews with participating scientists.

Chapter 5 consists of a sample appli- cation of those results utilizing a very simple water chemistry model and a data base provided by the New York State DEC. The data from the elicitation interviews, however, can be easily coupled with other data bases and water chemistry models in order to yield different predictions of fish population damage due to acidification.

This report does not connect fish population response to acid deposition. The independent variable throughout was the pH of Adirondack ponded waters. No attempt was made to estimate the effect of acidification upon stream populations. Because stream fishing is important in the Adirondacks, future regional effects estimates should address this area as well.

The sensitivity of these fish habitats to acidification is a function of many factors, and is different from sensitivity recorded for the same species in bioassay experiments. For example, while brook trout are known to be resistant to acidifcation effects, much brook trout habitat is vulnerable to acidification because of its morphometric and bio- geochemical characteristics.

All use some variant of subjective probability eiicitations. The only exception is the use of statistically derived confidence intervals. However, the use of statisical confidence intervals for dimensioning uncertainty around acid rain estimates suffers from two severe shortcomings. First, they are based on a set of statistical assumptions and model specifications e.

These techniques, based on Bayesian methods, should be explored whenever sample data is available. The elicitation technique used in this project estimated the range of possible effects with very little information on the shape of the probability distribution within this range. This process was selected because of the extreme uncertainty characteristic of acid deposi- tion caused fish population effects.

It might be possible, however, to estimate more accurately the form of the probability distribution within the lower and upper boundaries of the predicted effects. Recall that the project segmented the range between the lower and upper bounds of the effects by calculating the midpoint and then asking the scientist to indicate which seg- ment of this range was more likely.

More information could be obtained by having the scientist rank each segment within the range from most Ukely to least likely, as shown on line C of Figure Another alternative would be to have the scientist directly estimate a probability distri- bution for effects at each pH level. This would require the scientist to estimate, for each pH level, the precise probability associated with each effects outcome or range of outcomes. In this project, the effects outcome was a reduction in fish habitat.

This elicitation technique was not used in the project because the estimation of a precise cumulative probability distribution proved to,be extremely difficult for the scientist given the current state of knowledge.

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