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Home My WebLink AboutEffect of Timing & Rate of Fertilization to Ground Water 1982 J J~ J. J I J I I. 1 1 . . EFFECT OF TIMING AND RATE OF FERTILIZATION . ~' it" ON , POTATO GROWTH AND NITRATE LEACHING TO GROUND WATER 1 1 1 1 1 1 1 1 REPORT S2 ,_.......~ CENTER FOR ENVIRONMENTAL RESEARCH CORNELL UNIVERSITY ITHACA, NEW YORK 14853 J J ] J 1 ]i ] ]1 ]I ]I ]1 JI ]I ] . . EFFECT OF TIMING AND RATE OF FERTILIZATION ON POT A TO GROWTH AND NITRATE LEACHING TO GROUNQ WATER Report 52 Working Paper I August 1982 Computer Work and Documentation By: Nancy M. Trautmann Mary Jane Heather Keith S. Porter ~.....,..... With Graphics By: Donna C. Curtin JI )1 JI JI JI Center for Environmental Research Cornell University Ithaca~ New York 148B , ]i I 1-- . iJ . . Preface ] The question of fertilization timing and rate was initially brought up as an issue of concern in Southold by members of the Southold Citizen's Advisory j Committee. Bud c:;ybulski and other Committee members expressed concern during several discussions that atthough Cornell University research had shown lowered fertilization rates to be optimal for potato growth and ground-water 11 JI quality, educational efforts by Cornell and Cooperative Extension have JI insufficiently encouraged farmers to adopt these lower rates since the completion of the research. JI Current practice is for many farmers to apply a heavy dose of fertilizer at planting to provide insurance against losses induced by spring rainfall. When JI heavy rains have occurred in recent years, however, farmers have been JI concerned that perhaps additional fertilizer needs to be applied to replace the losses despite the insurance. The end result is very high fertilization incurring JI high risks of leaching losses to ground water. After heavy rains in the spring of 1982, Joe Sieczka from the Long Island "'10.__.. JI Horticultural Research Laboratory, and Dale Moyer from Suffolk County JI Cooperative Extension, requested that we analyze nitrate losses from the root zone. This report represents the results of W ALRAS simulations of nitrate JI leaching under various fertilization practices. These results confirm the earlier research showing that split application of reduced amounts of fertilizer reduce 31 leaching losses while providing sufficient nitrogen for optimal potato production. J/ The work was conducted under the auspices of the New York State JI Department of Environmental Conservation as part of the Fertilizer, Herbicide, , . ]I and Pesticide Demonstration Project funded by the U.S. Environmental Protection Agency. JI ~I' .~J . . JI 1 jl Nitrate contamination of water recharging Sovlhol~ I..'~ ..:... ........1 be reduced by changing agricultural fertilization pracllCM.. T ,;,,"c": . ......." practice for potato farming is to apply an average 01 19210::-:: *('. .... il..'~" 200 lb N/ Ac) at the time of planting in April or May. l~c.&uw" ,.at C;" ~...... "I fertilizer is applied before active plant growlh, the "'ttOlt"'" ., ."r....h susceptible to leaching rather than plant uptake, result'"~ In .,..,.....: ru...ty expense to the growers as well as contamination of the ground ,....1.... After an extensive study of nitrogen needs for optlm,,1 pol"t" i,ro..ltl J :11 jl jl consistent with ground-water quality on Long Island, \Iel~H\~ff 11':17101 ] recommended that Suffolk County growers reduce their lerllliUliOll rolle 10 about 170 kg N/ha (150 lb N/Ac). Meisinger also endorsed 'phltln~ l~le JI LJI '-JI :] fertilizer application so that a portion is applied at planting and lhe rern.llnder in five or six weeks when plant growth is active. Field research condUl:ted by Cornell University has shown that such changes result in greatly reduced r..tes of nitrate leaching to ground water (e.g. Porter, 1977). Using the Water and Land Resource Analysis System IW..\UL\S', 'Ne analyzed five fertilization schemes using climate and soil conditi~r;s_t)'''lCal 01 Southold. These five schemes were meant to represent a range Irom current -JI practice to opti mal practice, as follows: ] a) 220 kg N/ha at planting b) 192 kg N/ha at planting 165 kg N/ha at planting 110 kg N/ha at planting, and 55 kg N/ha 5 weeks later 55 kg N/ha at planting, and 110 kg N/ha 5 weeks later -:I c) d) ] e) -:I -:I As expected, our analyses showed less nitrogen leaching when less was applied (Figure O. The largest decrease occurred between 220 and 192 kg N/ha (200 and l751b N/Ac), with smaller differences in leaching rates between the :.' ,5-":&~3:;,:,',,~ . . 2 FIGURE 1. RELATIONSHIP BETWEEN FERTILIZATION RATE AND TOTAL NITRATE LEACHED FOA TYPICAL POTATO FIELDS IN SOUTHO(.O, L.I., N.Y. 14 12 10 TOTAL 8 NITRATE LEACHED (MOIL) 8 4 2 55-110 .. 110-55" 165 192 FERTILIZER APPLIED (KO HIH' ) 220 o .SJllLlT APPLICATION. AS UI'LAINED IN THE TEXT .....--.. other fertilization schemes. The 220 kg N/ha fertilization rate provides more nitrogen than the plants can assimilate. Some of this excess is broken down through denitrification, but the remainder leaches to ground water in concentrations well above the drinking water standard of 10 mg/I. According to Meisinger (1976), no significant increase in potato yields occurs for fertilization rates above 168 kg N/ha (150 Ib N/Ac), so the lower rates are advantageous economically as well as environmentally. Split application further reduced the amount of nitrate leaching, resulting , . in a recharge concentration of 8.2 mg/l (Figure 2). For the 10 mg/l drinking water standard to be met 90% of the time, 6 mg/I should be used as the .~__ _:""_'__._L.~~_ . . 3 . . .. . C' . FIGURE 2: COMPARISON OF NITRATE LEACHING FROM HEAVY FERTILIZATION AT PLANTING vs. LIGHTER FERTILIZATION WITH SPLIT APPLICATION C' . C' PRECIPITATION "~, " '~\~i, , .. .- .. .. .1 ., . , .j 'I I II :1 :1 ....-.-. :1 ------------ ----- ----- ---- - ----------'---------- ;1 :1 :1 :1 :1 :1 J ..,.."."-....".~.~' '.F"i".".~~",..,_,!, -~~' . . 4 maximum target concentration for planning purposes. The split application schemes came the closest to meeting this goal, as shown in Tabl~ 1: Fertilizer At Planting (kj1; N /ha) 220 192 165 110 5.5 Table I Comparison of Recharge Quality Under Various Fertilization Schemes , Fertilizer' After .5 Wks (kj1; N/ha) Nitrate Concentration of Recharge Water (mj1;/!) 14.2 9.6 9.2 8.2 8.2 .5.5 110 I Our simulations showed no significant difference between applying 2/3 of the fertilizer at planting .and 1/3 later, and vice versa, so either could be acceptable environmentally. Growers, however, would probably prefer to apply 2/3 rather than 1/3 at planting in case weather conditions..Rrohibit making the second application on schedule. In conclusion, current fertilization practices on Southold potato farms tend to be higher than needed. Split application of 16.5 kg N/ha can maintain potato yields while decreasing nitrate leachate concentrations to levels more compatible with the drinking water standard. Possibilities for action include the following: · Implementation of an educational program by Cooperative Extension (and others?) to publicize the benefits of reduced fertilization. . . . . 5 . Monitoring of ground water below selected fields to which different fertilization practices have been applied to trace movement of nitrate from the root zone. . Continued research by the Long Island Horticultural Research Laboratory on optimal fertilization rates for both crop , production and ground-water quality, particularly considering implications for other nutrients. . Analysis of other sources of nitrate pollution, including turf grass as well as on-site sewage disposal systems, to put farm practices into an overall context. .. References Meisinger, J.J. 1976. Nitrogen application rates consistent with environmental constraints for potatoes on Long Island. Search Agriculture, Vol. 6, No.7. Cornell University Agricultural Experiment Station, Ithaca, N.Y. ,_.,..,.. Porter, K.S. 1977. Agricultural practices: policy implications. pp. 47-65 In W.R. Kerns (ed.) Public policy on ground water quality protection. Virginia Water Resources Research Center, Blacksburg, Virginia. . .. ..