Ridge, Moldboard, Chisel, and No-Till Effects on Tile Water Quality beneath Two Cropping Systems

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1 Agriculturl nd Biosystems Engineering Publictio Agriculturl nd Biosystems Engineering 1997 Ridge, Moldbord, Chisel, nd No-Till Effects on Tile Wter Qulity beneth Two Cropping Systems Rmeshwr S. Knwr Iow Stte University, Thoms S. Colvin United Sttes Deprtment of Agriculture Dougls L. Krlen United Sttes Deprtment of Agriculture Follow this nd dditionl works t: Prt of the Agriculture Commo, Bioresource nd Agriculturl Engineering Commo, Hydrology Commo, nd the Wter Resource Mngement Commo The complete bibliogrphic informtion for this item cn be found t be_eng_pubs/684. For informtion on how to cite this item, plese visit howtocite.html. This Article is brought to you for free nd open ess by the Agriculturl nd Biosystems Engineering t Iow Stte University Digitl Repository. It hs been epted for inclusion in Agriculturl nd Biosystems Engineering Publictio by n uthorized dministrtor of Iow Stte University Digitl Repository. For more informtion, plese contct digirep@istte.edu.

2 Ridge, Moldbord, Chisel, nd No-Till Effects on Tile Wter Qulity beneth Two Cropping Systems Abstrct Soil coervtion tillge systems, including ridge-tillge, often reduce surfce wter contmintion by pesticides becuse soil erosion nd surfce runoff re reduced. However, the effects on losses through subsurfce dringe tile re somewht uncertin. Our field study quntified the effects of four tillge prctices in continuous corn (Ze mys L.) nd corn-soyben [Glycine mx (L.) Merr] rottio on herbicide nd nitrte N losses in tile dringe wter. Fertilizer nd pesticide ppliction methods were uniform for ridge, moldbord, chisel, nd no-till systems. Pesticide nd nitrte N leching losses were significntly ffected by crop rottion. Tillge prctice hd little influence on nitrte N nd pesticide losses to the subsurfce dringe wter within corn-soyben rottion. However, ridge-till nd no-till resulted in lrger losses of trzine thn the moldbord plow nd chisel bsed systems under continuous corn. Tillge system did not ffect the timings of pek tile flow ourrences, lthough pek tile flow volume ws ffected by tillge, presumbly becuse ech system bd its own mcropore system relted to preservtion or nnul destruction of biopores by tillge. Corn yields were significntly higher under corn-soyben rottion thn with continuous-corn for ll tillge prctices. These results indicte tht continuous corn production is not n environmentlly sustinble prctice for this re becuse it resulted in higher nitrte N leching losses to groundwter, received higher N- pplictio, nd resulted in lower corn yields thn the corn-soyben rottion. The results lso reinforce the need for studies on chemicl plcement, rte, nd timing for vrious tillge prctices to reduce tile dringe losses of griculturl chemicls. Diiplines Agriculture Bioresource nd Agriculturl Engineering Hydrology Wter Resource Mngement Comments This rticle is from Journl of Production Agriculture 1 (1997): , doi:1.2134/jp Rights Works produced by employees of the U.S. Government s prt of their officil duties re not copyrighted within the U.S. The content of this document is not copyrighted. This rticle is vilble t Iow Stte University Digitl Repository:

3 Published April 19, 213 Reserch Appliction Summries Soil nd Wter Qulity Ridge, Moldbord, Chisel, nd No-Till Effects on Tile Wter Qulity beneth Two Cropping Systems R. S. Knwr, I: S. Colvin, nd D. L. Krlen Problem Pesticide nd nitrte losses into groundwter quifers from some soil nd crop mngement prctices re decresing the wter qulity. Literture Summry Agriculturl chemicls pplied on or ner the soil surfce cn be rpidly trported to deeper soil depths nd into shllow groundwter. One process through which this ours is movement through tile dringe wter. The type of tillge nd cropping system used cn influence the mount of these mterils tht cn be lost from griculturl fields. However, the effects of these prctices, especilly t the field le re not well understood. A better understnding of soil mngement prctices is therefore needed to protect surfce nd groundwter qulity. Chemicl leching losses cn be minimized by using prctices like bnding of herbicides nd multiple N pplictio to decrese herbicide nd nitrte concentrtio in the soil wter, but it is difficult to control the volume of tile dringe wter. One exception is tht ridge-till nd no-till prctices cn be used to increse the mount of crop residue left on the soil surfce. This influences rinfll prtitioning between surfce runoff nd subsurfce dringe, which cn increse grichemicl movement with subsurfce dringe s surfce runoff would be decresed. Ridge-till cn increse crop yield on poorly drined soils by creting ridges tht re wrmer nd drier thn soils tht re not tilled. Ridge-till cn lso hve economic dvntgesbecuse it combines tillge nd herbicides to control weeds. Comprison between ridge-till nd other coervtion tillge prctices is needed to determine the effects of these prctices on dringe wter qulity. The min objective for this study ws to quntify the effects of four tillge prctices in continuous com nd com-soyben rottio on herbicide nd nitrte N loss to tile dringe wter. Study Deription This study ws conducted t Iow Stte University s Northest Reserch Center ner Nshu, on the Kenyon-Clyde-Floyd soil ssocition. The site hs 36 1cre plots tht hve hd subsurfce dringe system itlled for more thn 14 yr. Tile lines re spced 95 ft prt t n pproximte depth of 4 ft. Ech plot hs tile l i e s long the edge nd one in the middle tht hs been intercepted nd connected to n individul sump to mesure the volume of wter flow. Approximtely.2% of the tile dringe wter is collected every time wter is pumped for nitrte N nd herbicide nlyses. Tillge tretments were fll moldbord plow, fll chisel plow, ridge-till nd notill. Continuous-cornnd corn-soyben rottio were compred for ll tillge Full ientific rticle from which this summry ws written begi on pge 227 of this issue. J. Prod. Agric., Vol. 1, no. 2,

4 , Applied Question tretments. Crops were plnted in rows with six row plnter. Becuse the combine hd 9-in. wheel bse, four of every six rows hd wheel trck during the seson. Continuous corn plots received 18 lb N/cre ech yer, while rotted corn received 15 lb N/cre s nhydrous mmoni injected between rows. Continuous-corn tretment received lchlor (2. lb ilcre) plus trzine (2.5 lb.i./cre) plus Counter for rootworm control. Corn in the corn-soyben rottion received lchlor (2. lb ilcre) plus cynzine (2.5 lb.i./cre) nd no iecticide. Soyben plots received lchlor (2. lb.i./cre) plus metribuzin (.4 lb ilcre). All herbicides nd iecticides were brodcst. Cultivtion, even with the no-tillge tretment, ws used to help with weed control. Dringe wter smples were nlyzed for lchlor, trzine, cynzine, metribuzin, nd nitrte N. Will doption of ridge-tillge for continuous corn or corn-soyben rottio reduce nitrte N nd pesticide loss to tile dringe wter? The yers 1988 nd 1989 were extremely dry, nd the rinfll ws well below norml. The yers nd were unusully wet, with totl rinfll mounts of more thn 41 nd 38 in., respectively. The yer hd dry spring nd wet fll with totl rinfll of in. These rinfll ptter cused ll tile lines to flow through most of the growing seso of,, nd. Tile flow hd similr reltiohips mong tillge systems in nd, indicting tht tillge systems did not ffect the totl tile flow volumes. Lrger tile flows ourred with continuous-corn thn with the corn-soyben rottion. On the verge, no-till nd ridge-till systems hd the highest pek tile flows for most growing seson storms regrdless of crop. Higher pek tile flows under the ridge-till nd no-till probbly ourred becuse mcropores (worm or root holes nd nturl frctures) re not destroyed or disturbed by primry tillge. With continuous corn, verge subsurfce dringe fiom no-till ws significntly higher thn from moldbord plow plots, but for the com-soyben rottion, tile flows were not sttisticlly different for vrious tillges. A different mcropore system ppers to be opertive under ech crop rottion nd tillge tretment. Losses of nitrte N were much greter under continuous corn thn under corn-soyben rottion. In, they rnged fiom 26 to 68 lb/cre, while in, the highest loss of 96 lblcre ws bout 5% of the nnul mount pplied. Less nitrte N ws lost from the corn-soyben rottion thn from continuous corn becuse N ppliction rtes were lower nd less fkquent nd yields were higher. Atrzine losses were greter thn for cynzine or metribuzin. The rpid ppernce of trzine, lchlor, cynzine, nd metribuzin t high concentrtio in subsurfce dringe wter shortly fter rinfll suggests tht preferentil movement of these herbicides ourred in this silty soil overlying lomy glcil till. Ridge-till nd no-till prctices, especilly with continuous corn, pper to preserve mcropore network more thn chisel or moldbord plowing. We conclude tht, to reduce nitrte N nd herbicide losses to dringe wter, ridge-till nd no-till prctices should be used in combintion with 2-yr corn-soyben rottion. 188 J. Prod. Agric., Vol. 1, no. 2,1997

5 Reserch Soil nd Wter Qulity Ridge, Moldbord, Chisel, nd No-Till Effects on Tile Wter Qulity beneth Two Cropping Systems R. S. Knwr,* T. S. Colvin, nd D. L. Krlen Soil coervtion tillge systems, including ridge-tillge, often reduce surfce wter contmintion by pesticides becuse soil erosion nd surfce runoff re reduced. However, the effects on losses through subsurfce dringe tile re somewht uncertin. Our field study quntified the effects of four tillge prctices in continuous corn (Zeumys L.)nd corn-soyben [Glycine mr (L.) Merr) rottio on herbicide nd nitrte N losses in tile dringe wter. Fertilizer nd pesticide ppliction methods were uniform for ridge, moldbord, chisel, nd no-till systems. Pesticide nd nitrte N leching losses were significntly ffected by crop rottion. Tillge prctice hd little influence on nitrte N nd pesticide losses to the subsurfce dringe wter within corn-soyben rottion. However, ridge-till nd no-till resulted in lrger losses of trzine thn the moldbord plow nd chisel bsed systems under continuous corn. Tillge system did not ffect the timings of pek tile flow ourrences, lthough pek tile flow volume ws ffected by tillge, presumbly becuse ech system bd its own mcropore system relted to preservtion or nnul destruction of biopores by tillge. Corn yields were significntly higher under corn-soyben rottion thn with continuous-corn for ll tillge prctices. These results indicte tht continuous corn production is not n environmentlly sustinble prctice for this re becuse it resulted in higher nitrte N leching losses to groundwter, received higher N-pplictio, nd resulted in lower corn yields thn the corn-soyben rottion. The results lso reinforce the need for studies on chemicl plcement, rte, nd timing for vrious tillge prctices to reduce tile dringe losses of griculturl chemicls. S URFACE OR NEAR SURFACE pplied chemicls my be rpidly trported through soil nd into shllow groundwter (Everts nd Knwr, 1994; Iseee et l., 1988; Knwr et l., 1985, 1988, 1993). This rpid movement of chemicls is evidenced by preferentil flow of solutes R.S. Knwr, Dep. of Agric. nd Biosystems Eng.; T.S. Colvin nd D.L. Krlen, USDA-ARS Ntionl Soil Tilth Lb., Iow Stte Univ., Ames, IA 511. Iow Agric. nd Home Econ. Exp. Stn. J. Pper no. J Project no. 33. This reserch ws fimded by the Leopold Cent. for Sustinble Agric., Ames, IA, nd the USDA-CSRS Project on Mngement Systems Evlution Ares (MSEA). Received 2 Feb Torresponding uthor (rsknwr@istte.edu). Published in J. Prod. Agric. 1: (1997). (Czpr et l., 1994; Knwr, ; Knwr et l., 1993; Everts nd Knwr, 1994). It is generlly presumed tht griculturl chemicls found in groundwter were pplied to the soil, moved through it, nd deposited into quifers primrily by mss flow. To develop soil nd crop mngement systems tht protect groundwter qulity, vrious groundwter contmintion mechnisms need better understnding. Specific mechnisms for groundwter contmintion re often unknown becuse pesticide nd N leching re ffected by mny fctors (Splding et l., 1989; Johon nd Kross, ; Hllberg, 1989; USGAO, ). The mount of subsurfce dringe is one fctor ffecting these processes. The locl hydrologic blnce generlly controls this volume, lthough some tillge prctices (Knwr nd Bker, 1993) cn minimize chemicl leching losses by decresing herbicide nd nitrte N concentrtio in the soil wter. Plcement of grichemicls in soil zones tht re fvorble for root growth nd where wter does not umulte my lso reduce the potentil for leching to groundwter (Allmrs et l., 1993; Hmlette et l., ; Blylock nd Cruse, ; Cly et l.,, 1994; Lowery et l., 1993). Tillge prctice nd crop sequence cn hve mjor impct on surfce wter nd groundwter contmintion by pesticides nd N, but their impct, especilly t the field nd wtershed les, re not thoroughly understood. One fctor on which tillge hs profound effect is the mount of crop residue left on the soil surfce. This influences prtitioning of rinfll between runoff nd infiltrtion nd cn lso ffect grichemicl movement. Vrious coervtion tillge prctices, including ridgetill nd no-till, hve been studied to help develop better mngement prctices for grichemicls ( D o h et l., 1993; Weed et l., 1995). No-till generlly minti soil structure, while conventionl tillge destroys most of the root chnnels nd other preferentil pthwys for movement of wter nd grichemiclsto deeper soil lyers. Interest in ridge-tillge is incresing becuse, by controlling the number of continuous mcropores which cn become preferentil flow pths, movement of wter nd grichemicls to deeper soil lyers my be reduced. Furthermore, by creting ridges tht dry more quickly nd re wrmer thn if soil is not tilled, crop yield on poorly drined soils is often incresed. (Reeder, ). Ridge-till is lso more economicl thn other tillge systems becuse it J. Prod. Agric., Vol. 1, no. 2,

6 combines tillge nd herbicides to control weeds (Reeder, ). A creful comprison between ridge-till nd other coervtion tillge prctices is needed to determine environmentl benefits t the field le. For this study, the objectives were to quntify herbicide nd nitrte N losses in tile dringe wter, crop growth, grin yield, nd N umultion when four tillge prctices were imposed on 1-cre continuous corn nd corn-soyben rottion plots. MATERIALS AND METHODS This study ws conducted t Iow Stte University's Northest Reserch Center in Nshu. The soils t this site re Floyd lom (fine-lomy, mixed, mesic Aquic Hpludolls), Kenyon silty-cly lom (fine lomy, mixed, mesic Aquic Hpludolls), nd Redlyn lom (fine-lomy, mixed, mesic Aquic Hpludolls). These silty soils re modertely well to poorly drined, lie over lomy glcil till (USDASCS, 1977), hve 3 to 4% orgnic mtter, nd belong to the Kenyon-Clyde-Floyd soil ssocition. Generlly, preillinoisn glcil till units of 2 ft in depth overlie crbonte quifer used for wter supply, but in some res bedrock is lmost ner the surfce. These soils hve sesonlly high wter tbles tht vry from 2 to 5 ft below the surfce, nd thus benefit from subsurfce dringe. The study site hs 36 1-cre plots nd hd coistent tillge nd cropping prctices for 14 yr (Krlen et l., ) before this study ws conducted. Subsurfce dringe tile were itlled bout 4 ft deep t spcing nd hd lso been in plce for more thn 14 yr. Ech 1-cre plot hs tile line pssing through the middle of the plot nd tile line t ech of the two borders. Middle tile lines of ll the plots were intercepted nd connected to individul sumps for mesuring subsurfce dringe (tile flow) nd collecting wter smples for chemicl nlyses. The middle dringe tile of ech plot dri n re of bout.5 cre nd is free from cross contmintion from ll four sides s this tile dri only the middle hlf of ech one cre plot. To monitor tile flow on continuous bsis, ech tile sump hs 11 volt effluent pump, wter flow meter, nd n orifice tube to collect wter smples for wter qulity nlysis. The wter flow meters were connected to dtloggers for recording tile flow dt. For wter qulity smpling, n orifice tube ws designed to deliver bout.2% of the tile wter into smpling bottle ech time dringe wter ws pumped from the sump. Tillge tretments were moldbord plow, chisel plow, ridge-till, nd no-till systems. The moldbord plow plots were plowed in the fll to depth of 6 to 8 in., nd then disked in the spring to depth of bout 4 in. Chisel plow plots were chiseled in the fll nd cultivted in the spring. The ridge-till plots hd the top of the ridge removed by the plnter, but ridges were reestblished t height of 6 to 8 in. during the finl cultivtion. All tillge systems, including no-till, received one or two psses of cultivtion for weed control nd ertion. Crop sequence tretments included continuous-corn nd corn-soyben rottio. Crop rottion, tillge, nd chemicl ppliction prctices hve been in plce since Corn-soyben rottion nd continuous corn tretments were replicted three times in 228 J. Prod. Agric., Vol. 1, no. 2, 1997 rndomized complete block design on 36, 1-cre plots. Both the corn nd soyben phses of rottion were plnted ech yer. Corn hybrids include Pioneer' 3747 in 1985 nd 1986, Pioneer 3782 in 1987, nd Golden Hrvest H2343 from 1988 through. Soyben vrieties include Corsoy in 1977 nd 1978, Hrcor in 1979 nd 198, Vickery in 1981, Corsoy 79 from 1982 through 1986, Elgin in 1987, Hrdin in 1988, nd Snds of Iow from 1989 through. Crops were plnted in 3-in. rows with six row plnter. Becuse the combine hd 9-in. wheel bse, four of every six rows hd wheel trck during the seson. All crops were cultivted during the seson for weed control. Continuous corn plots received 18 lb N/cre ech yer, while corn-soyben rottion plots received 15 lb N/cre when corn ws plnted. No N ws pplied to soybe. The continuous-corn tretment received lchlor (2. lb.i./cre) plus Atrzine (2.5 lb.i./cre) plus Counter (phosphorodithioic cid S[[ 1,l-dimethylethyl)thio]methyl]O,O-diethyl ester) for rootworm control. Corn grown in rottion received lchlor (2. lb.i./cre) plus cynzine (2.5 Ib.i./cre) nd no iecticide. Soyben plots received lchlor (2. lb dcre) plus Metribuzin (.4 lb.i./cre). Anhydrous mmoni ws knifed-in just before plnting. The nhydrous mmoni pplictor knife ws stndrd knife bout.75 to 1 in. wide. All herbicides nd iecticides were brodcst fullwidth on ll tillge plots. In ddition to composite smples, tile wter smples fiom ll tillge plots were mnully collected for nitrte N nlysis pproximtely three times per week when tile lines were flowing to observe time bse vritio in the nitrte N concentrtio. Composite tile wter smples for pesticides were tken weekly nd fter every mjor rinfll (>1 in.) within 6 d of pesticide ppliction; during the reminder of the yer, tile wter ws smpled weekly for grichemicls when tile lines were flowing. After ny mjor rin storm, both nitrte N nd pesticide were smpled to understnd the concepts/chrcteristi of preferentil flow. Wter smples were refrigerted until nlyzed in the lb. Dringe wter smples were nlyzed for lchlor, trzine, cynzine, metribuzin, nd nitrte using GC/MS (gs chromtogrphy/mss spectroopy) procedures operting in the selected ion mode. Wter smples were nlyzed for herbicides by dding propzine surrogte to 25-mC smple, then pssing the smple through n Anlytichem Interntionl C-18 crtridge', which dsorbs orgnic compounds, including the herbicides of interest. The herbicides nd surrogte were eluted from crtridge with 2 ml of ethyl cette tht contined internl stndrds. The herbicide concentrtio in the ethyl cette solution were quntified by mss spectrogrphy. The minimum detection limit for herbicides in wter smples ws 2 ppm (.2 mgkg).i. Wter smples were spectrophotometriclly nlyzed for nitrte N using Lcht Model AE ion nlyzer' (Lcht Itruments, Milwkee, WI).Results were reported in units of mgl L for nitrte N. Six plnts were chosen rndomly from ech 1-cre plot t physiologicl mturity or growth stge R6 (Ritchie nd Trde nd compny nmes re used for the benefit of reders nd do not imply endorsement by the USDA nd Iow Stte University.

7 Hnwy, 1984) to determine N umultion by the corn crop; hrvested plnts were dried t 15 F, weighed, chopped, ground to pss No. 34 (.2 in. or.5-mm) stinless steel reen, nd nlyzed for totl N using Crlo-Erb Model NCS' 15 (Hke Buchler Itruments, Ptterson, N.J.) dry combustion nlyzer. Totl eril biomss nd N umultion were computed bsed upon mesured plnt popultion (26 5 plntdcre ). Grin yields for ech plot were mesured with modified commercil combine. To clculte N removl, grin smples in were ground nd nlyzed for N concentrtion using the Crlo-Erb in. Removl for 1988 through ws estimted by ssuming the sme grin N concentrtion s in. RESULTS AND DISCUSSION The yers 1988 nd 1989 were extremely dry, with rinfll well below the long-term verge of 3 in., but nd were unusully wet yers, with totl rinfll mounts of more thn 41 nd 38 in., respectively. In, spring ws dry nd fll ws wet with totl nnul rinfll of in. These rinfll ptter cused ll tile lines to flow through most of the,, nd growing seso. More preferentil flow smples were collected in ( wet yer fter two dry yers), thn in either or. Drier wether in 1988 nd 1989 my hve left lrge number of root nd worm holes intct from previous yers s mcropores in. Soil crcking nd shrinkge could lso be eqully importnt following the drought yers of 1988 nd 1989 in cusing lrge volumes of preferentil flow in. Tile flow hd similr reltiohips mong tillge systems for ll three yers. Pek tile flow usully ourred within the sme dy tht mjor rinfll event ourred, indicting preferentil movement of wter through mcropores. Bjorneberg et l. (1996) estimted time to pek flow from.5 h to bout 6 h fter the beginning of mjor rinfll for this site. Lrger tile flows were observed with continuouorn thn with soyben-corn rottion in (Fig. 1 nd 2). Similr reltiohips in tile flows were observed in nd. On the verge, no-till nd ridge-till systems resulted in the highest pek flows in tile wter for most growing seson storms regrdless of cropping system (Fig. 1 nd 2). The moldbord plow tretment resulted in the lowest tile pek flow, especilly in continuous corn. Lrger pek flow under ridge-till nd no-till conditio results when mcropores (worm or root holes nd nturl fictures) re not destroyed or disturbed. In solute trport experiments, Singh nd Knwr () reported higher degree of preferentil flow in no-till soil colum. Tillge nd corn-soyben rottion ffected the volume of subsurfce drii flow (Tble 1). Under continuous corn, the yerly verge driige from no-till plots ws significntly higher thn fiom moldbord plow plots (Tble 1). Subsurfce driige under the corn-soyben rottion, however, ws comprtively lower thn under continuous corn for ll tillge systems except ridge-till. A different mcropore system ppers to be opertive under ech crop rottion nd tillge tretment. With corn-soyben or soyben-corn rottio, tillge tretments resulted in different tile dringe ptter, but the differences were not lrge. Plots with corn- Tble 1. Tillge nd crop rottion effects on tile dringe flow, verge nitrte N concentrtio in tile wter, nd totl nitrte N loss witb tile wter. Yer Rin (in.) Rottiont CPS 7.2b b MP RT NT Subsurfcedringe (in.) 3.5c 7.lb b lb l b Ob S.7b b Nitrte N concentrtioin dringe wter (ppm) 54b 28b b b 33b b S 12 21b 44c l 25c b 24c 12b ll 16c 39c 19c Il 23bc b 22c Ilb 9 14C Nitrte N loss with dringe wter (lb/cre) I Avg - Av. t Il 29 7S 56 1O ll Vlues followed by the Sme letters in the rows re not stgtisticlly different(sas, 1985). CC = continuous corn; SC = soyben fter corn; CS = corn fter soyben. CP = chisel plow; MF' = moldbord plow; RT = ridge-tillge; NT = no-tillge. soyben rottio resulted in lower tile wter pek flows in comprison with continuous-corn production system for ll tillges (Fig. 1 nd 2). Ridge-till nd no-till systems gve higher subsurfce dringe with continuous corn thn chisel nd moldbord plowing. The verge dily nitrte N concentrtio in tile wter were influenced by smpling dte, tillge, nd rottio (Fig. 3 nd 4). The yerly verge nitrte N concentrtio in tile wter from moldbord plow plots were coistently higher thn with the three other tillge systems for continuous corn rottion. This could be due to the fct tht plowing elimintes the mcropore structure nd infiltrtion wter hs to pss through soil micropores s mtrix flow (rther thn preferentil flow) llowing more time for wter to crry soil nitrte N down to tile lines (Singh nd Knwr, ). Fig. 3 nd 4 show tht nitrte N concentrtio in tile wter from no-till plots were lowest, indicting tht nitrte N ws bypssed by preferentil flow through mcropores. (Bjorneberg et l., 1996; Knwr et l,. 1985; Knwr, ). J. Prod. Agric., Vol. 1, no. 2,

8 g c5 C Y.% 2.- e!.423 -zix Q 1 Soyben-Com,.24 P.16 d.8 Fig. 1 Averge dily tile flows under rotted corn in s function of tillge (CP = chisel plow, MP = moldbord plow, RT = ridgetillge, NT = no-tillge). 23 J. Prod. Agric., Vol. 1, no. 2,1997

9 + * +++ Continuous Corn, 31- B ort v 8.2 ANT :: C z $? 4 -.-i?i E p U Dy of Yer Fig. 3. Averge dily nitrte N concentrtioin tile flows under continuouorn in s function of tillge (CP = chisel plow, MP = moldbord plow, RT = ridge-tillge, NT = netillge). -E - n B s ' P 4 : + + Soyben-Corn, Dy of Yer Fig. 4. Averge dily nitrte N concentrtioin tile flows under soybeorn rottion in s function of tillge (CP = chisel plow, MP = moldbord plow, RT = ridge-tillge, NT = netillge). J. Prod. Agric., Vol. 1, no. 2,

10 The 3-yr ( to ) verge nitrte N concentrtio in tile dringe wter were significntly higher under continuous corn thn under corn-soyben rottion for ll tillge tretments (Tble 1). This undoubtedly reflects the higher rte of N fertiliztion pplied to the continuous corn plots. Averge nitrte N concentrtio in dringe wter from the moldbord plow plots were significntly higher thn from the no-till nd ridge-till plots under continuous corn. Higher nitrte N concentrtio in tile wter from moldbord plowed plots thn ridge-tillge or no-tillge tretments my hve resulted from plowing nd disking eliminting the mcropore structure, resulting in conditio where wter must pss through the soil profile ording to the concepts of piston flow (mtrix rther thn preferentil flow) (Knwr, ). Lower nitrte N concentrtio in tile wter from no-till plots my hve resulted from more wter moving through mcropores thn the N fertilizer bound soil mtrix or tht less N ws subjected to leching becuse N minerliztion rtes my hve been less in no-tillge thn conventionl tillge tretments. Of concern ws the fct tht in, nitrte N concentrtio in nerly ll tile flow smples exceeded 1 ppm (the USEPA sfe drinking wter stndrd; USEPA, 1993) regrdless of tillge prctice nd crop sequence. Sesonl totl nitrte N losses in dringe wter rnged from 27 to 96 lb/cre for compred with 4 to 18 lb/cre in (Tble 1). Losses of nitrte N were much greter under continuous corn thn under corn-soyben rottion. Losses for rnged from 26 to 68 lb/cre. The highest nitrte N loss of 96 Ib/cre in, bout 5% of the mount pplied, ws from no-till plots under continuous corn. In, the highest nitrte N loss of 68 Ib/cre ws observed from chisel plow plots. Although nitrte N concentrtio from continuous corn plots were greter under moldbord plow thn under no-till, the totl nitrte N losses through tile dringe wter were greter under no-tillge nd chisel plow systems becuse of greter volume of wter moving through the soil, lthough differences were not significnt (Tble 1). The nitrte N losses in were much lower thn in erlier yers becuse lrger nitrte N losses were observed in two extremely wet yers of nd. Sttisticlly, there ws no difference of nitrte N loss between tillge tretments within rottio. There is lrge decrese in nitrte N loss when moving from continuous corn to corn-soyben rottion becuse N ppliction rte on rotted corn ws 15 Ib/cre, compred with 2-yr totl ppliction of 36 Ib/cre under continuous corn. Uptke of residul N following the corn yer by soybe lso contributed to lower losses of N with crop rottion. Also, the long-term effects of soil orgnic mtter with rottio hve to be evluted for nitrte N leching nd sustinbility of production systems s there is possibility of differentil N minerliztion (or immobiliztion) mong different tillges. Also, the sources of N in tile wter includes soil orgnic mtter, rin wter, nd pplied N fertilizer. The mount of trzine losses to subsurfce drin wter were greter (lthough sttisticlly noignificnt) thn with the other herbicide, lchlor, lthough there ws difference in their ppliction rtes for different crop rottio (Fig. 5). Also, no-till nd ridge-till hd greter trzine losses under continuous corn thn moldbord plow nd chisel plow systems but these differences were not sttisticlly significnt. Most of this leching ourred in the first month fter herbicide ppliction (Knwr et l., 1993 ). Weed et l. (1995) observed tht for ll yers nd tillges, 84% of lchlor, 7% of trzine, nd 82% of the metribuzen present in the soil profile were retined in the top 4 in. up to 48 d fter ppliction. This provided opportunity for the pond-.2 Atrzine Loss.15 h E P 3 v c G Alchlor Loss.5 Cynzine Loss Metribuzin Loss Continuous Corn Rotted Corn Rotted Corn Rotted soybe Fig. 5. Averge yerly pesticide loss with dringe wter under vrious tillge systems s function of crop rottio for 3 yr (-). Sme letter on the top of the brs indictes tht tillge effects were not significnt (CP = chisel plow, MP = moldbord plow, RT = ridge-tillge, NT = notillge). 232 J. Prod. Agric., Vol. 1, no. 2, 1997

11 Tble 2. Tillge nd crop rottion effect on eril biomss umultion (dry mtter in to per cre) nd corn grin yield (bushels per cre t 15.5% wter content) t Nshu for 1988, 1989,,, nd. Biomss t mturity (R6). tondcre Rottiont Fctor Interction Rottion Tillge Corn grin yield, bdcre Tillgef CP NT MP RT CP NT MP RT I I I I I I4 I42.3'.8** 6 6' cv (%) n.9.8' 8.4.; IO 13. 9** 8 9** 8** 7** 4 n.9 4** " 3** 3** 4 *, **, = LSD nd level of significnce.5,.1, nd not significnt, respectively. t CC = continuous corn; SC = soyben fter corn; CS = corn fter soyben. 1CP = chisel plow; MP = moldbord plow; RT = ridge-tillge;nt = no-tillge. Tble 3. Tillge nd cropping system effect on eril N umultion from 1988 through. Whole plnt N umultion, Ib/cre Rottiont Tillget Avp. CP NT MP RT CP NT MP RT I1s Fctors Interction Rottion Tillge CV(%) 1 IO ' 12 n ' 1 19 n.9 12" 17 *, **, 11s= LSD nd level of significnce.5,.1, nd not significnt, respectively. t CC = continuous corn; CS = corn fter soyben. 1CP = chisel plow; MP = moldbord plow; RT = ridge-tillge;nt = no-tillge. ed wter to mix herbicides present in the surfce lyer of soil nd crry it preferentilly to the top of the wter tble nd eventully move it through the tile lines. Since more preferentil flow cn our under no-till nd ridge-till conditio, lrger herbicide leching losses were lso observed for these two tillge systems thn with moldbord plow nd chisel plow systems, lthough differences were not sttisticlly significnt. Although ridge-till nd no-till systems pper to give higher cynzine nd metribuzin losses with rotted corn nd rotted soybe, respectively, these differences re not sttisticlly different from ech other. Aeril biomss umultion for the 5 yr verged 7.6 nd 7.2 tondcre ech yer for rotted nd continuous corn, respectively. Cropping system differences were coistent (Tble 2), but sttisticlly significnt only for. Tillge effects were sttisticlly significnt in nd becuse ridge-till nd no-till both umulted less eril biomss thn the chisel or moldbord plow tretments. The cropping system x tillge interction ws not sttisticlly significnt Production differences in boveground biomss were lso reflected in grin yields (Tble 2), which for 1988 through verged 143 nd 126 bdcre for rotted nd continuous corn, respectively. Except for, corn yield ws significntly higher when grown in rottion with soy- ben thn when grown continuously (Tble 2) for ll tillge prctices. Averge no-till nd ridge-till yields were lower thn for chisel or moldbord plow tretments, primrily becuse of the poor performnce of those tretments under the continuous corn. Yerly totl N umultion (Tble 3) in the eril biomss verged 132 nd 129 lb/cre for the rotted nd continuous corn, respectively. The tillge prctice significntly ffected totl N umultion in 1989 nd, nd when verged for 5 yr. This ourred becuse no-till nd ridgetill tretments hd significntly lower biomss nd N umultion thn the other tillge tretments. Crop rottion hd no significnt effect on eril N umultion. Annul N removl in the grin (not shown) verged 84 nd 73 Ib/cre, respectively. Trditionlly, N use efficiency would hve been clculted s the rtio of grin N to fertilizer N. In this study, those vlues rnged fiom 52 to 56%. However, ISN studies demotrte tht ctul fertilizer N recovery by corn crop rnges from 13 to 33% (Snchez nd Blckmer, ). Minerliztion of N from soil orgnic mtter ounts for the remining 67 to 87% of crop uptke. Fertilizer N tht ws not ounted for by crop uptke ws presumbly dded to soil N pools where it ws subject to immobiliztion, stbiliztion, denitrifiction, or leching. This incorportion into soil N pools emphsizes the importnce of soil temperture differences due to tillge systems, which ffect minerliztion nd my hve greter effect on the ppernce of nitrte in tile wter thn the preferentil flow processes. SUMMARY AND CONCLUSIONS This study indictes tht leching potentil of nitrte N nd herbicides to shllow groundwter is ffected by tillge nd crop rottion when the loding rte is high nd the grichemicl ppliction is uniform. The rpid ppernce of trzine, lchlor, cynzine, nd metribuzin t high concentrtio in subsurfce dringe wter, shortly fter rinfll, suggests tht preferentil movement of these herbicides ourred in this silty soil overlying lom glcil till. Aeril biomss yield, grin yield, nd N umultion mesurements demotrte tht continuous corn grin production is not n environmentlly sustinble prctice for this re. J. Prod. Agric., Vol. 1, no. 2,

12 Under these study conditio, continuous corn production resulted in higher nitrte N leching into the tile lines, which led ultimtely to surfce wter or groundwter resources. Ridge-till nd no-till prctices pper to preserve mcropore network better thn chisel or moldbord plowing. Use of best chemicl plcement prctices, which we did not evlute in this study, my hve the potentil to correct some wter qulity problems ssocited with griculturl chemicls. Becuse no-till in continuous corn production performed most poorly (in terms of corn yields) in these studies, lterntive prctices should be incorported into t lest 2-yr corn-soyben rottion to eure the prctices re both economiclly vible nd environmentlly benign. Economic eptbility of these systems will depend on the frmers' bility to reduce inputs, nd hence costs, reltive to the moldbord nd chisel plow systems. 234 J. Prod. Agric., Vol. 1, no. 2, 1997