Guidelines for Using Conservation Tillage Under Furrow Irrigation

Transcription

1 Technicl Report TR August 2015 Agriculturl Experiment Sttion Guidelines for Using Conservtion Tillge Under Furrow Irrigtion Second Edition Erik Wrdle Troy Buder Clvin Person College of Agriculturl Sciences Deprtment of Soil nd Crop Sciences Extension

2 Guidelines for Using Conservtion Tillge Under Furrow Irrigtion, Second Edition Erik Wrdle, Reserch Associte, Deprtment of Soil nd Crop Sciences, emil: Troy Buder, Senior Reserch Associte/Extension Specilist, Deprtment of Soil nd Crop Sciences, emil: Clvin H. Person, Professor/Reserch Agronomist, Deprtment of Soil & Crop Sciences, Agriculturl Experiment Sttion, Western Colordo Reserch Center, 1910 L Rod, Fruit CO 81521, e-mil: clvin.person@colostte.edu Acknowledgments: Primry funding for this project ws through Colordo NRCS-CIG grnt, nd dditionl resources were contributed by The Fort Collins nd Big Thompson Conservtion Districts, the Agriculturl Chemicl nd Groundwter Protection Progrm nd Colordo Corn. We would lso like to cknowledge expertise nd guidnce provided by Phil Westr nd Neil Hnsen nd dediction from project grdute student, Jordn Driscoll. Our thnks to ARDEC stff for their ssistnce with fieldwork. Thnk you to Tyler Cozzens for his review of frm budget nd economic dt. Lstly, we would like to express our sincere grtitude to members of our project dvisory committee, especilly our industry nd frmer coopertors. Mention of trde nme or product does not imply endorsement of product or brnd t the exclusion of other similr products or brnds. Any mention of trde nme or product is for the convenience of the reder. Colordo Stte University is n equl opportunity/ffirmtive ction institution nd complies with ll Federl nd Colordo Stte lws, regultions, nd executive orders regrding ffirmtive ction requirements in ll progrms. The Office of Equl Opportunity is locted in 101 Student Services. In order to ssist Colordo Stte University in meeting its ffirmtive ction responsibilities, ethnic minorities, women, nd other protected clss members re encourged to pply nd to so identify themselves. Cover photos: Crop residue in growing corn. Photos by Erik Wrdle Technicl editing, design, nd lyout by Lindsey Middleton

3 Contents Introduction 3 Mnging Surfce Crop Residue 4 Seedbed Preprtion 5 Soil Fertility nd Nutrient Mngement 5 Equipment 6 Plnting 7 Cultivtion 7 Weed, Insect, nd Disese Mngement 7 Irrigtion 8 Wter Qulity 10 Hrvesting 11 Post-Hrvest Field Mngement 11 Crop Rottions 12 Limittions for Using Conservtion Tillge with Furrow-Irrigtion 13 Economics 14 Mking Conservtion Tillge Work 16 Selected References 17

4 Chopping residue. Photo by Erik Wrdle

5 Introduction This guidebook is intended to inform growers, representtives in gribusiness, government gency personnel, nd others of the potentil for using conservtion tillge in furrow-irrigted conditions. While the guidebook is not exhustive, it ws designed to be of sufficient detil nd scope to inform the reder of the vrious cropping nd mngement possibilities for successfully using conservtion tillge technology on furrow-irrigted croplnd. Informtion from two Colordo Stte University experiments on conservtion tillge is incorported throughout the publiction. One experiment ws conducted t the Western Colordo Reserch Center (WCRC) t Fruit (Figure 1) nd with cooperting growers on the Western Slope of Colordo. The other is ongoing t the Agriculturl Reserch Development nd Eduction Center (ARDEC) nd with cooperting frmers long the northern Front Rnge of Colordo. Tillge is defined s soil-stirring opertions performed for the purpose of producing crops. Trditionl prctices on furrow-irrigted fields involve multiple energy-consuming tillge opertions intended to loosen soil, bury residue, smooth nd level soil surfces, nd crete suitble seedbed. However, these systems leve the soil surfce uncovered nd vulnerble to wind nd wter erosion during much of the yer, when wether conditions re often most conducive to soil loss. Residue, often clled trsh by frmers, cn cuse furrow dms during irrigtion, incresing dvnce times nd limiting irrigtion uniformity while incresing lbor. Cool spring soil tempertures in undisturbed soil my limit erly seson plnt growth nd slow stnd estblishment. Disese nd insect pest concerns in some crops hve lso limited widespred doption. Recent developments in plnting nd tillge system technologies nd new crop vrieties offer more options for lleviting cool spring soil tempertures nd successfully deling with crop residue during plnting nd irrigtion. These tillge systems, coupled with more ccurte nd economicl Globl Positioning Systems (GPS), re gining widespred cceptnce in Colordo nd prts of the Western Gret Plins nd the Intermountin West. The use of conventionl or clen tillge often results in over-tilled soils, cusing the loss of orgnic mtter nd the brekdown of soil structure. Clen tillge promotes soil erosion nd nutrient loss, cretes soil compction, increses soil moisture loss, nd increses lbor nd production costs. The best tillge system is one tht chieves profitble crop production long with environmentl nd socil needs while incurring the lest cost. Tillge need only promote good soil helth nd sustined crop production. No tillge opertion cn be justified by trdition or hbit. Conservtion tillge is defined s ny tillge nd plnting system in which either: t lest 30% of the soil surfce is covered by residue following plnting, or t lest 1,000 pounds of smll grin residue is mintined per cre on the soil surfce. Frmers in mny furrow-irrigted res hve been reluctnt to dopt conservtion tillge. This is result of concerns ssocited with tilling, plnting, irrigting, nd hrvesting in fields with surfce crop residue. Conservtion tillge prctices re different thn the conventionl tillge methods frmers re ccustomed to using on furrow-irrigted croplnd. Furthermore, conservtion tillge technologies developed for rin-fed or sprinkler-irrigted conditions re not generlly directly pplicble to furrow-irrigted conditions. A mjor concern bout conservtion tillge under furrow irrigtion is the uncertinty of being ble to furrow-irrigte fields contining surfce residue. Frmers my lso be reluctnt to mke the encompssing chnges, including the necessry finncil nd mngement investments, tht re needed to dopt conservtion tillge successfully on their furrow-irrigted croplnds. 3 Conservtion tillge is n umbrell term tht includes tillge systems such s strip tillge, mulch tillge, no-till, zero tillge, minimum tillge, slot plnting, till-plnt, rotry till, ridge till, zone tillge, nd others. Figure 1. Pinto bens plnted following corn t the Western Colordo Reserch Center t Fruit. Photo by Clvin Person However, given tht more frmers re incorporting conservtion tillge on their sprinkler-irrigted lnd, they re lso looking for options to utilize the sme equipment on flood-irrigted frmlnd (Figure 2). Growers must hve sufficient justifiction to consider dopting conservtion tillge technology. There re numerous resons frmers my wish to dopt conservtion tillge on furrow-irrigted croplnd, including: Conservtion tillge typiclly reduces production costs by eliminting severl field opertions, nd it reduces soil erosion cused by wind nd wter, mking crop production more sustinble. Conservtion tillge cn mintin yields by reducing the loss of fertile soils nd nutrients. In certin environments, conservtion tillge cn improve yields by reducing erosion. Filling gullies nd smoothing fields becuse of erosion cn be expensive nd detrimentl to long-term field productivity. Unchecked erosion cn reshpe

6 Options for mnging residue: Rotting crops Spreding evenly Removl by biling Moving residue to dry rows or pushing to the side Grzing Figure 2. Incresed soil moisture storge in n erly seson corn stnd often elimintes the need to irrigte crop up. Photo by Phil Westr Figure 3. Biling off corn residue. Photo by Erik Wrdle fields s topsoil is moved to the bottom of the field, creting flt fields, or cuse incresed slopes t the bottom of the field when soil is moved off-site, mking surfce irrigtion more difficult. The resons nd motivtions for dopting conservtion tillge my differ mong frmers nd loctions, but the net result is usully positive. Mnging Surfce Crop Residue How crop residues re mnged ffects the production of subsequent crops in terms of yields nd the ese nd bility to perform vrious field opertions. When conducting field opertions, frmers should perform ech opertion s precisely s possible. They must consider how prticulr field opertion influences subsequent opertions. This is especilly importnt when mnging surfce residue on furrow-irrigted lnd. Severl principles of mnging surfce crop residue hve generl ppliction to most furrow-irrigted conditions. Crop rottion hs numerous benefits nd is one of the most effective tools for mnging residue in conservtion tillge systems. A system such s continuous grin corn production cretes lrge mounts of residue ech yer, nd while this cn be effectively mnged (s will be discussed below), it is not recommended. Rotting high residue crops with lower residue crops (i.e., dry bens, sugrbeets) cn gretly simplify mngement. Smll grins lso work well in these systems. Crop residue should be spred nd mintined s evenly s possible cross the entire field, becuse other prctices cn be performed much more redily when surfce crop residue is uniform. Uniform surfce residue in fields is prticulrly importnt when plnting nd cultivting. Non-uniform surfce residue will cuse equipment to perform inconsistently nd numerous djustments my be required s conditions chnge cross field. Residue mngement begins t hrvest, nd using combine with chff chopper nd spreder to distribute residue will mke subsequent opertions esier. There re two min pproches to hndling the size of residue. Work done on the West Slope showed tht crop residue should be mintined in pieces tht re s lrge s prcticl. Lrge pieces of residue nchor to the soil more redily nd re less subject to movement by wind nd irrigtion wter thn smller pieces of residue. Disking nd chopping residue into fine pieces my not lwys be desirble. The type of crop nd the residue produced by vrious crops influences how well residue stys in plce. For exmple, corn residue is less subject to movement by wind nd irrigtion wter thn whet residue. Front Rnge cooperting frmers recommended sizing residue in order to fcilitte moving it to desirble loction in the field. This cn be done in number of wys. Following high residue crops (like grin corn) chopping nd bling portion of stlks helps to size mteril nd remove 4

7 Figure 4. Row clening. Photos by Jordn Driscoll some of the residue from the system (Figure 3). Some growers perform shllow disking opertion when conditions re dry in order to slice residue without burying it. Once residue is sized, it cn be moved into non-irrigted row (in every other row irrigtion) or pushed to the side of the beds with ditcher, cultivtor, or row clener (Figure 4). It is importnt to consider tht residue removl will tke nutrients out of the system tht would be otherwise vilble for crop production. Loss of nutrients nd soil crbon cn hve n impct on the long -term productivity of field, requiring incresed fertilizer costs; therefore, mix of residue mngement options is recommended. Seedbed Preprtion A suitble, uniform soil structure must exist cross the entire field re to provide fvorble environment for seed germintion nd subsequent plnt growth. While this my be chievble with conservtion tillge prctices, dditionl opertions my be needed to crete idel conditions for plnt growth nd irrigtion. Two importnt spects should be considered during seedbed preprtion when using conservtion tillge under furrow irrigtion: proper soil preprtion nd the considertion of wter ppliction when creting furrows. The first spect reltes to the condition of the seedbed. The field surfce must llow plnting to be performed without difficulty. The seedbed must be sufficiently uniform so seeds re plnted t consistent depth cross the field nd plced into the soil to obtin good seed-to-soil contct. At ARDEC one of the lrgest impediments to the conservtion tillge system ws the difficulty in prepring uniform seedbed. Plnting on n eroded bed, into compcted soil, or on uneven surfces creted problems with seed plcement. Poor emergence, errtic plnt stnds, vulnerbility to lodging, nd potentil yield loss re often consequences of poor seed plcement. Strip tillge llows for preprtion of suitble seedbed nd minimizes problems ssocited with seed plcement s mentioned bove. Reducing compction nd ensuring mellow but firm seedbed is one of the key dvntges of strip tillge (Figure 5). The strip till opertion cn significntly fltten nd reshpe old beds, nd some soil nd residue move down into the furrow. Beds nd furrows will usully need to be reformed prior to the first irrigtion of the seson. The second spect of proper seedbed preprtion when using conservtion tillge under furrow irrigtion concerns wter ppliction. Furrow shpe nd size needed for irrigting under conservtion tillge re often not the sme s those used for conventionl, clen-tillge. Furrows needed for conservtion tillge re typiclly 5 Figure 5. Strip till opertion - proper djustments to the implement re criticl; keep in mind this is seed bed preprtion, not rough tillge opertion. Photo by Erik Wrdle formed during seedbed preprtion. Considertion should be given to furrow size nd shpe to ensure they will be dequte throughout the irrigtion seson. Soil Fertility nd Nutrient Mngement Nutrient mngement in high residue, conservtion tillge systems is not significntly different thn mngement in other modern crop production systems, but some djustment is required. Most of the Best Mngement Prctices promoted in Colordo re pplicble in ll tillge systems nd my be more importnt under conservtion tillge. For exmple, routine soil smpling to determine residul soil fertility is vluble tool for determining crop needs for supplementl nutrients. In conservtion tillge, soil is no longer thoroughly mixed, nd tking representtive soil smple requires ccounting for vribility from the bnding loction, irrigted vs. non-irrigted rows, nd other fctors. Split ppliction of fertilizer (including strter t plnting, deep plcement, nd side-dress nitrogen nd phosphorus s needed) works well in these systems to produce profitble crop nd reduce potentil environmentl impcts. The strip till opertion cn lso be used for deep plcement of portion of crop fertilizer needs (Figure 6). Proper fertilizer plcement is criticl, prticulrly with lower quntity of mobile nutrients like phosphorus. Plcing

8 Figure 8. Four-row strip tiller used t WCRC-Fruit. Photo by Clvin Person Figure 6. Strip till unit set up for deep plcement of liquid fertilizer. Photo by Erik Wrdle Figure 9. No-till grin drill developed t the Western Colordo Reserch Center t Fruit. Photo by Clvin Person Figure 7. Plnting corn through residue on the previous yer s beds. Photo by Erik Wrdle nutrients where plnt roots cn rech them throughout the growing seson cn help reduce environmentl losses nd increse nutrient use efficiency. When using conservtion tillge, significnt surfce residue cn led to incresed nitrogen immobiliztion. This is generlly short-term problem nd cn be redily mnged by pplying dditionl nitrogen fertilizer during the estblishment phse of conservtion tillge. Deeper plcement of nitrogen is one pproch tht mitigtes the need for incresed fertilizer relted to immobiliztion. In ddition, higher residue environments will hve cooler erly seson soil tempertures, which my excerbte micronutrient deficiencies erly in the growing seson. The use of conservtion tillge under furrow irrigtion hs prompted concerns tht incresed nitrogen leching my occur. This concern rises out of the potentil for reduced irrigtion uniformity to increse deep percoltion. Bsed on reserch results obtined t WCRC- Fruit from two seprte experiments, incresed nitrogen leching is not problem when using conservtion tillge systems under furrow irrigtion, prticulrly if growers use good irrigtion wter mngement prctices. An experiment ws conducted during 1996 nd 1997 t WCRC-Fruit with five nitrogen ppliction rtes from zero to 268 pounds of nitrogen per cre nd three ppliction timings. The three ppliction timings were: 1) ll nitrogen bnd pplied t plnting, 2) 1/3 of the nitrogen bnd pplied t plnting nd the remining 2/3 bnded in whet before the first node 6 nd side-dressed in corn t the five- to seven-lef stge, nd 3) ll nitrogen bnded post-emergence in whet before the first node nd ll sidedressed in corn t the five- to seven-lef stge of development. All tretments were pplied to both crops. Results from this experiment indicted tht nitrogen rte nd timing pplictions could be quite flexible without dversely ffecting corn yields or creting environmentl problems relted to nitrte leching. Soil type is n importnt considertion for mking nutrient mngement decisions relted to crop production nd reduced environmentl impcts. Corse textured sndy soils re more prone to leching thn finer textured cly soils, mking mngement to prevent leching reltively more importnt for fields with sndy textures. Equipment Specilized nd specilly-djusted equipment is often necessry when using conservtion tillge technology under furrow-irrigted conditions. Crops grown with furrow-

9 irrigtion often hve high yields, nd with mny crops, not ll plnt mteril is hrvested or removed from the field; this leves lrge mounts of crop residue in the field fter hrvest. It is importnt to remember crop residue mngement begins t the time of hrvest, nd ensuring residue is spred uniformly will mke things esier during the next irrigtion seson. The equipment must be cpble of hndling lrge quntities of surfce residue when performing required opertions. These opertions include forming nd shping beds nd furrows, plnting, cultivting, ripping, chiseling, nd pplying fertilizers (Figures 7-8). Equipment developed nd used in conventionlly mnged cropping systems my not be suitble for use in conservtion tillge under furrow irrigtion. For exmple, most commercil grin drills will not operte properly when used for conservtion tillge under furrow irrigtion. A grin drill tht is suitble for furrow-irrigted conditions must hve djustble drive wheels to trck irrigtion furrows (Figure 9). Becuse furrow widths chnge depending on the crop nd grower preferences, wheels must be movble to ccommodte different distnces between furrows. The grin drill must lso hve djustble seed openers to llow proper seed row plcement cross the width of the bed. Grin drills for conservtion tillge in furrow-irrigted conditions lso must hve multiple tool brs to stgger seed openers so residue will flow through the plnter, or drill must specificlly ccommodte high residue plnting. Plnters tht llow for individul djustments to ccommodte vrious row spcings, seed spcings, nd individul seed opener plnting depths re essentil for conservtion tillge under furrow irrigtion. Modern row crop plnters generlly work well in conservtion tillge on furrows without mjor djustments. Front mounted row cleners re usully needed to move residue off the seed bed. Some growers hve hd success combining multiple opertions into single pss. For exmple, with dequte horsepower, it is possible to operte strip till unit followed by shovels to rebuild beds long with plnter directly behind it. Multiple tool brs should lso ccommodte coulters for pplying fertilizers or shovels for forming furrows. Adjustments to the trctor nd the down force springs of the plnter re necessry to chieve proper seed plcement. Plnting Conservtion tillge systems under furrow irrigtion hve spects tht differ from those encountered in clen-tillge conditions. Plnters must be hevy enough so seed openers nd plnter units penetrte through residue nd plce the seed t the proper depth nd in uniform position long the length of the row. Setting the trctor three-point down drft force nd djusting the plnter unit down force springs, if vilble, cn help chieve proper seed plcement. Surfce residue must flow through the mchine without ctching, drgging, nd ccumulting, cusing the plnter to plug. Plugged plnters crete residue piles in the field tht must be spred, which increses lbor costs, cn dversely ffect plnt stnds, nd cuses difficulty performing other field prctices such s irrigting. Proper seed plcement on the bed is essentil. Some growers plnt directly through the previous yer s row nd hve hd good success. If following corn or nother crop tht leves significnt stlk nd root bll, removing these cn cuse some issues, both t plnting nd during irrigtion. At ARDEC, seed ws plnted pproximtely three to four inches offset from the old crop row, leving stlks nd root blls mostly undisturbed (see bck cover photo). Experience hs shown tht plnting in wet soils is more of chllenge thn 7 plnting in dry soils. Wet conditions mke it difficult for openers to penetrte through residue. Also, closing the seed row behind the plnter unit to chieve good seed-to-soil contct is much more difficult in wet soils. This is less of concern in strip tillge. These issues tend to present themselves erly in the trnsition to reduced tillge nd will be of less concern the more yers field hs been in conservtion tillge. In some cses, residue cover nd soil conditions in fields under conservtion tillge for few yers will llow field ccess nd plnting in wetter conditions thn plowed ground. Cultivtion Similr to plnting, cultivting with lrge mounts of surfce residue present cretes chllenges tht differ from cultivting under clen-tillge conditions. Surfce residue must flow through the cultivtor freely, without ctching, drgging, or creting clumps or piles. If the cultivtor hs row crop shields, they my need to be rised or removed to prevent these problems. Rolling cultivtor tools re generlly preferred, even when only moderte mounts of surfce residue re present. Opertors must be creful tht residue nd soil do not indvertently cover or lodge plnts. A timely cultivtion cn move residue round plnts or in other res to crete mulch lyer tht will provide weed control, retin soil moisture, nd hold topsoil. During the lst cultivtion of the seson, furrows nd beds should be formed dequtely to ccommodte irrigtion needs for the reminder of the growing seson. Weed, Insect, nd Disese Mngement Perennil weeds, such s field bindweed, my require specil ttention nd mngement when using conservtion tillge (Figure 10). With good mngement strtegies, conservtion tillge my be more effective in controlling some perennil weeds thn hs been the cse with conventionl tillge systems. This is prticulrly evident given the reltively recent vilbility of herbicide tolernce in severl crops.

10 Methods of Weed Control Dense, vigorous stnd Proper irrigtion Adequte soil fertility Crop rottion Adpted vrieties Good soil dringe Cultivtion/tillge Residue mngement Plnting time nd methods Compnion crops Weed-free seed Weed control before plnting Mowing Burning/flming Herbicides Biologicl (insects) Cover crops In non-irrigted systems, shifts in weed species fter chnging tillge systems re common nd should be expected under irrigted conditions s well. Desirble weed, insect, nd disese mngement strtegies will be similr to prctices tht re effective in controlling pests, no mtter wht tillge system is used. Clen-tillge systems depend hevily on mechnicl mens of weed control, but when using conservtion tillge, other options must be considered. Some mechnicl weed control occurs when forming beds or cultivting, but it is importnt to use n pproprite integrted pest mngement pproch, including pesticides, conservtion tillge, crop rottions, nd geneticlly-engineered crop vrieties. The incresing presence of herbicide resistnt weeds my mke weed control in ll systems more chllenging. A dynmic herbicide nd weed mngement progrm tht incorportes residul nd contct products will be needed to keep these weeds under control. Figure 10. Perennil weeds cn be chllenge when converting to conservtion tillge; however, fter four yers of conservtion tillge nd sound weed mngement pln, the bindweed tht ws in this field is gretly reduced. Photo by Erik Wrdle Pest pressures chnge with incresed crop residue. Diseses tht overwinter in soil my require crop rottion or resistnce to mnge. Disese nd insect pressure my be more of concern thn weed mngement under conservtion tillge. Significnt surfce residue nd undisturbed soil cn be excellent hbitt for some pest popultions. At ARDEC, Goss s wilt infesttions hve been seen in ll tillge tretments, but higher prevlence hs been found in the conservtion tillge systems. Crop rottion cn help with both insect nd disese issues tht my be excerbted by conservtion tillge. Field monitoring nd regulr crop scouting re essentil to identify problems erly so dequte time is vilble to select nd schedule suitble responses. Irrigtion Conservtion tillge cn ffect numerous spects of furrow irrigtion (Figure 11). Wter infiltrtion rtes were 24% higher in 1991 nd 50% higher in 1992 t WCRC-Fruit with conservtion tillge thn with conventionl mngement. Reserch in other prts of the U.S. hs lso shown tht 8 infiltrtion rtes re higher with conservtion tillge thn with clen tillge under furrow irrigtion. Irrigtion wter dvnce times my be longer with conservtion tillge thn with conventionl tillge (Figure 12). Advnce time is the time is tkes irrigtion wter to move down the furrow. Residue dms nd mellow soil cn slow the dvnce of wter down the field nd ffect irrigtion uniformity from furrow to furrow. At WCRC-Fruit, irrigtion wter dvnce times were 37% longer in 1991 nd 25% longer in 1992 with conservtion thn with conventionl tillge. However, this is not lwys the cse, nd depending on soil type, surfce compction, nd other fctors, dvnce times my be fster thn with clen tillge. At ARDEC in 2012, irrigtion dvnce times in both conservtion tillge tretments were significntly shorter thn the time required in the plowed ground during the first irrigtion of the yer. This ws due in prt to the severely dry spring nd the moisture tht ws lost during tillge opertions. The conservtion tillge plots were not powder dry nd were firm, nd erly seson irrigtions were more effective. Extremely long dvnce times in the fully tilled ground hd number of negtive impcts, including pumping costs, leching of wter nd nutrients t the top of the field, nd poorly irrigted crop t the bottom end of the field. These impcts were voided using conservtion tillge systems. Soil wter content is often higher, especilly t plnting, when conservtion tillge is used compred to clen tillge. Soil wter content verged 17% higher for corn, 17% higher for soyben, nd 27% higher for dry ben with conservtion thn with clen tillge t WCRC-Fruit. Higher infiltrtion rtes nd higher soil wter content in conservtion tillge my llow for irrigting less often thn with clen tillge. Irrigting less often nd more efficiently using conservtion tillge cn sve wter nd the lbor needed to irrigte crops. Erly seson soil moisture content t ARDEC ws significntly different between tillge tretments in ech cropping yer. At

11 plnting, in the top six inches of soil, the conservtion tillge plots hd more wter. This incresed surfce moisture llowed the seed to germinte nd begin root development prior to n irrigtion. In three of the four study yers, this erly development llowed the crop to tp deeper soil moisture nd grow without irrigtion until cultivtion in the striptill tretment. Not hving to irrigte mens not turning well on erly or being ble to use vilble wter on higher priority field. Furrow strem size, the growing crop, field slope, soil type, residue quntity nd type, field length, soil roughness, nd soil compction ffect furrow irrigtion. Attempting to chieve uniform infiltrtion long the length of the furrow in field, while minimizing the mount of runoff, necessittes mnging s mny of these fctors s much s possible. For exmple, when irrigting in furrows contining lrge mounts of residue, grower my need to increse the furrow strem size to compenste for the effects cused by the residue. Cre must be tken not to increse strem size too much, s excess flow my erode beds, cuse incresed dmming, nd offset sediment reduction benefits. Furrows my need to be lrger thn norml. Furrows my lso need to be smoother with fewer soil clods nd more compcted to lower furrow roughness to mintin dvnce times t n cceptble rte. Growers need to ctively mnge the mount of residue in the furrow. When too much residue is in the furrow, Irrigtion djustments with conservtion tillge include: Altered irrigtion flow rte Lrger furrows Potentil for irrigting less often due to incresed soil moisture Figure 11. Conservtion tillge contributes to incresed infiltrtion nd soil wter content during irrigtion. Photo by Erik Wrdle Minutes Inches/( CT * MT ST CT MT ST Figure 12. Left: Irrigtion dvnce times in minutes for 2011 nd 2012 shown s n verge of ll irrigtions; Right: Soil moisture t plnting zero to six inches. (CT - conventionl till, MT - minimum till, ST - strip till; lowercse letters indicte sttisticl differences) * Does not include first irrigtion of the yer for

12 some of it my need to be moved to lternte rows or between rows using cultivtor tools or row cleners where it won t interfere with irrigtions or growing plnts. With corn residue, prcticl mngement technique is to move residue to lternte furrows during seedbed preprtion or just prior to plnting. Moving residue too erly cn leve it vulnerble to being moved by wind bck into the prts of the field where it will cuse problems for plnting nd irrigting. The irrigtion fter plnting cn be done in these lternte furrows tht hve lower mounts of residue. Once crop plnts re big enough, residue in other furrows cn be mulched round the plnts, nd ll furrows cn be irrigted for the reminder of the growing seson. How the bottom of the furrow is mnged is importnt in controlling irrigtion wter infiltrtion. Residue in the furrow cn increse soil wetting in lterl direction. Therefore, to chieve cceptble dvnce times under conservtion tillge conditions, it my be necessry to hve slightly lrger furrow with smooth, compct, clod-free bottom. Under conservtion tillge, infiltrtion increses, nd if increses in infiltrtion re prtitioned towrd lterl wter movement nd less towrd verticl movement, the leching potentil my be reduced. When furrow roughness is too excessive under clen-tillge systems, infiltrtion will to be too high nd dvnce time too slow. A common frmer prctice to void this sitution is to drive furrows to reduce furrow roughness or run roller pckers. Reducing furrow roughness under clen-tillge systems smoothes the furrow by incresing soil compction nd eliminting or reducing soil clods. This pproch is eqully effective in conservtion tillge systems. Incresing the furrow strem size too much my crete n erosive energy tht cuses the wter to trnsport residue. Residue moving with the irrigtion wter my result in furrow dmming. Mintining residue size s lrge s prcticl nd using n pproprite tons/cre Sediment (g/l) Figure 13. Averge nnul sediment loss mesured t ARDEC for the three tillge systems, determined by multiplying sediment concentrtion in runoff smples by runoff mounts (numericl lbels indicte sttisticl differences) Irrig/on Induced Erosion strem size will reduce the likelihood of residue movement. To furrow irrigte successfully under conservtion tillge conditions, frmers must lern to blnce infiltrtion nd dvnce time, tking into ccount the dded effects creted by surfce residue. Mintining crop residue on or ner the soil surfce using conservtion tillge technology reduces furrow erosion during irrigting. In ddition, most frmers nd industry experts gree tht keeping residue on or ner the surfce mkes it much esier to mnge thn residue tht is buried. Deep disking or other opertions tht bury or incorporte crop residue nd mix it with soil cn mke it difficult to move nd mnge. Supplementl tillge opertions tht cn be kept Surfce Crop Residue (lbs/cre) Figure 14. The effect of surfce crop residue on the mount of sediment in irrigtion wter Conven/onl Minimum Strip Tillge System b only n inch or two deep will llow for more options for residue mngement. Furrow width ws found to be 8% wider under clen tillge in the first irrigtion nd 24% wider under clen tillge compred to furrows under conservtion tillge in the western Colordo experiment. Soil is more protected from the erosive energy of irrigtion wter when surfce residue is present. Thus, furrows re less subjected to the effects of erosion nd movement of soil when conservtion tillge is used compred to the wider furrows tht occur under clen-tillge cropping systems. Wter Qulity Sediment from irrigtion wter runoff cn contribute to wter qulity

13 degrdtion by trnsporting nutrients (nitrogen nd phosphorus), dsorbed pesticides, nd potentilly selenium to surfce wter bodies. As such, the Colordo Phosphorus Index Risk Assessment lists residue nd tillge mngement s Best Mngement Prctice pproprite to decrese the reltive potentil for off-site P movement for sites with high P runoff potentil (Shrkoff et l., 2012). An excessive mount of nutrients in surfce wter cn cuse excessive lge blooms which reduce sunlight penetrtion nd vilble oxygen, resulting in fish kills. Additionlly, irrigtion induced erosion results in vluble topsoil losses from fields nd slowly chnges the desired slope of grded fields. Conservtion tillge is one tool to help llevite sediment nd nutrient losses from surfce irrigted fields (Figures 13-14). Sediment loss is gretest in bre, smooth (no clods) soil compred to soils contining even smll mounts of surfce residue. The mount of residue required to reduce sediment loss cn vry bsed on number of fctors, but lrge quntities re not necessrily required. At WCRC-Fruit, using furrow residue simultor, incresing surfce residue beyond 3,570 lbs/cre for lom nd 1,800 lbs/cre for sndy soil did not further reduce sediment loss. Frmers who lern to mnge even smll quntities of surfce residue could reduce soil erosion on furrow-irrigted croplnd (Figures 15-16). In the ARDEC demonstrtion, residue up to 7900 lbs/cre fter plnting ws mnged to llow for successful irrigtions nd 40% reduction in sediment loss. Surfce soil texture hs significnt effect on sediment losses tht cn be expected when using conservtion tillge under furrow irrigtion. Reserch findings in Colordo indicte tht surfce residue in furrow-irrigted, field conditions is more responsive to mngement in finer textured soils such s loms nd clys thn in corse textured soils such s sndy loms. Nutrient losses in irrigtion runoff cn be reduced by conservtion tillge, but fertilizer plcement nd timing is Figure 15. Sediment-free irrigtion wter runoff t the end of the furrow nd into til ditch when conservtion tillge ws used in pinto ben production. Photo by Clvin Person Figure 16. Irrigtion wter runoff contining sediment t the end of the furrow when conventionl tillge ws used in pinto ben production. Photo by Clvin Person criticl in these systems. For exmple, concentrtions in totl phosphorus decresed in the ARDEC demonstrtion project, but soluble phosphorus did not decrese (Figure 17). Totl nitrogen ws not ffected, but soluble nitrogen, nitrte, incresed in the minimum tillge tretment. This ws becuse the fertilizer ws plced t shllower depth in the hrder soil furrow nd ws more vilble to being solubilized by irrigtion wter. Thus plcement is criticl in conservtion tillge systems. Bnding fertilizer in the dry furrow or ner the top of the irrigtion bed is one solution to reduce these losses. Additionlly, over time, phosphorus levels in conservtion tillge fields cn become strtified if P is surfce pplied since P is not mobile in soil (Figure 17). Higher P levels t the soil surfce hve resulted in incresed P loses in some studies in non-irrigted environments. Injection of P s bnd below the soil surfce cn mitigte these ffects nd cn lso lower the P rte required for profitble crop yields. 11 Hrvesting Reduced tillge systems require creful nd deliberte residue mngement beginning t hrvest. Growers should consciously consider how equipment nd equipment ttchments ffect crop residue. Stripper heders, strw spreders, strw choppers, nd chff spreders re few devices, long with their sizes, configurtions, number, nd djustments tht cn hve considerble impct on crop residue condition nd distribution in the field. Evenly distributed nd sized residue is esier to mnge thn piles, wind rows, or clumps. Avoid stopping in the middle of fields to prevent residue piles. Growers should consider how the type of equipment used, ssocited ttchments, nd the opertion nd performnce of equipment cn ffect future field opertions nd situtions. Proper mngement should be used to obtin uniform distribution of surfce crop residue cross the field. Growers should lso consider how wheel trffic from grin trucks, crts, nd trctors ffects residue nd soil conditions nd how subsequent field opertions my be ffected by wheel trffic tht occurs during hrvesting. Field trffic especilly cross beds should be minimized s much s possible. Post-Hrvest Field Mngement Once hrvest is completed, growers my be inclined to discontinue field work until next spring; however, the mnner in which fields re mnged following hrvest should be thoughtfully considered during nd fter hrvest. For exmple, once corn grin hs been hrvested, growers should decide if they should flil the residue or leve it stnding through the winter. At WCRC-Fruit, we hve found tht more residue is retined in the field when fliling is performed thn when corn stlks re left stnding during the winter. When corn stlks re left stnding during the winter, the wind removes leves nd other lighter

14 Mnging Crop Residue in Irrigtion Furrows A mg/l Phosphorus Concentr9on b c Soluble P Totl P Wter flows down furrow t rte (Q), cusing infiltrtion (i), dvnce time (t), nd wetted perimeter (p). The wetted perimeter is the distnce cross the furrow where wter contcts the soil (from rrow to rrow). B Conven,onl Till Minimum Till Strip Till Nitrogen Concentr8on Adding residue in the furrow slows wter flow (Q), increses infiltrtion (i), decreses dvnce time (t), nd increses wetted perimeter (p). mg/l b Nitrte Totl N A lrger furrow llows for n incresed wetted perimeter. C b Conven,onl Till Minimum Till Strip Till Figure 17. Averge concentrtion of nutrients in irrigtion runoff wter s ffected by tillge tretment (lowercse letters indicte sttisticl differences) mteril nd trnsports them out of the field, reltive to fliling the corn stlks. It is importnt to not chop stlks too low to the ground. Leving four to six inches of stlk stnding will help hold residue, cpture winter snow, nd reduce wind erosion potentil. Tller stlks will tend to cpture nd hold more snow thn shorter stlks, so soil moisture benefits should be weighed ginst prcticl mngement needs. Soil compction likely reduces yields more thn growers relize in ll types of cropping systems. Concerns hve been expressed bout soil compction problems developing when conservtion tillge is used in furrow-irrigted conditions. Bsed on field reserch conducted in western Colordo, soil compction ws similr between conservtion nd conventionl tillge in the three crops tht were studied over two-yer period, except for soyben in one yer where soil compction ws 23% higher with conservtion tillge thn with conventionl tillge. This sitution represents one in six cses tht soil compction ws ffected by tillge nd occurred fter only three yers of conservtion tillge. This finding indictes tht soil compction under conservtion tillge systems is potentil problem nd should be monitored similr to recommendtions currently mde for other tillge systems. At ARDEC, strip tillge hs worked well to llevite soil compction, especilly in the crop row. Hrvesting silge under wet soil conditions in 2013 cused significnt compction from equipment nd required deep ripping ll tire trcks in the field (Figure 18). While compction cn be concern, growers should keep in mind tht options, such s deep ripping, re vilble s needed to reduce the impct on crop productivity. Crop Rottions A number of crop rottions re possible when conservtion tillge is used under furrow irrigtion (Figure 12 19). Some crops nd some crop rottions re more conducive thn others for using conservtion tillge on furrow-irrigted lnd. A few crop rottion possibilities re presented in this publiction. Winter whet nd winter brley hve been successfully grown under furrow irrigtion using conservtion tillge following dry bens. Growers should be mindful of using herbicides in dry ben tht my crry over nd cuse dmge in smll grins. Dry ben residue should be spred s uniformly s possible cross the field during hrvest. Corn hrvested for silge followed by winter whet cn be ccomplished using conservtion tillge with furrow irrigtion. Hving plnter tht is cpble of plnting or tht cn be djusted to plnt in uneven conditions is importnt. Following plnting, furrows my need to be reshped. Corn for silge or corn for grin following lflf is common crop rottion tht

15 Mnging soil compction is criticl in ll tillge systems. growers hve ccomplished successfully. Alflf stnds cn be killed using pproprite herbicides, often Roundup for non-roundup Redy lflf, in the fll or spring. Grin yields of corn grown with conservtion tillge following lflf hve been comprble to yields grown using clen tillge. Fewer field opertions re needed when using conservtion tillge. This llows more time for frmers to be growing crops in the field insted of spending time doing field opertions. Double-cropping is the production of two crops in one growing seson. With conservtion tillge technology, it my be possible to develop double-cropping systems in furrow-irrigted res, where it hs not been possible under conventionl tillge systems. Limittions for Using Conservtion Tillge with Furrow-Irrigtion Developing conservtion technology for vrious crops grown under furrow irrigtion nd in different crop rottions requires considerble field reserch nd experience to identify the specific prctices tht perform well in prticulr cropping system. In some cropping systems, it my be difficult to mintin conservtion tillge over the long term, but in other situtions, it is possible to use conservtion continuously or t lest for severl yers. For exmple, re-leveling fields periodiclly tht hve been under conservtion tillge for period of time my be necessry to mintin uniform furrow-irrigted conditions. Lnd leveling is difficult when lrge quntities of surfce crop residue re present. Additionlly, crop species, crop rottions, nd cropping prctices vry considerbly cross the vrious furrow-irrigted regions of the U.S. Regionl nunces must be considered Figure 18. Silge hrvest in conservtion tillge. Photo by Troy Buder when developing nd using conservtion technology. Some crops in the rottion my require different row spcings. Chnging row spcings from yer to yer my be imprcticl nd thus limit the use of conservtion tillge. Considerble soil disturbnce occurs during hrvest of vrious crops such s pottoes, sugrbeets, onions, nd dry bens. These nd similr crops complicte the use of conservtion tillge nd my not llow continuous use of conservtion tillge. Growing no-till winter whet following grin corn presents chllenges when lrge mounts of surfce residue re present. Lrge mounts of surfce 13 corn residue cn cuse difficulty for whet seedlings to emerge nd cn cuse non-uniform plnt stnds. Also, t plnting if the soil is too wet the slot mde by the seed opener my not sel properly, leving the seed without dequte seed-to-soil contct. Plnting whet when the soil nd residue re dry usully results in the best outcome. Plnting pinto bens following winter brley s double-crop using conservtion tillge t WCRC-Fruit ws not successful. The problem encountered ws cused by incresed soil moisture. Becuse of the brley stubble, soil moisture incresed nd promoted development of root rot diseses in pinto ben, cusing reduced ben yields. Furthermore, during pinto ben Figure 19. Winter whet grown following silge corn t Fruit, Colordo. Photo by Clvin Person

16 hrvest, brley roots held onto clods tht were similr in size to ben seed. Lrge quntities of these smll clods were hrvested long with the pinto bens. Double-cropping pinto bens fter winter brley using conservtion tillge is not recommended. nd llows growers to benefit from soil moisture svings. The strip till system hd nerly $70 higher net return per cre thn conventionlly tilled ground. These results re similr to the previous work done t WCRC-Fruit. The study conducted t WCRC- Fruit in the erly 1990s compred conservtion with conventionl tillge in cropping system of corn, soyben, winter brley, nd dry bens under furrow irrigtion. Direct costs Fields tht re difficult to irrigte under clen-tillge conditions (long runs, flt fields, very sndy or grvelly soils) will likely be more chllenging with residue. Growers must be wre tht problems cn occur when using conservtion tillge under furrow irrigtion, nd they must seek to develop wys to void or overcome them. Growers should keep in mind tht it is lwys better to strt on few cres nd lern how to mke conservtion tillge work on their frm before scling up to more cres. Economics The economics of conservtion tillge systems hve been studied extensively in other prts of the country. The finncil benefits of reduced fuel use, fewer hours on trctors nd equipment, nd less lbor cuse mny growers to consider switching to conservtion tillge system. Of course, these reduced costs will not result in grower profits without mintining comprble yields nd qulity. In furrow-irrigted systems, dditionl considertions include irrigtion uniformity nd getting wter through the field without spending too much time in the field with shovel. Poor irrigtion nd incresed lbor costs if forced to wlk the field cn offset some of the finncil benefits of conservtion tillge. One of the gols of the experiment t ARDEC ws to keep detiled frm budget nd compre how conservtion tillge nd conventionl tillge behved fter three yers of continuous corn production. Dt collected included fuel use, lbor requirements, other input costs, crop yields, irrigtion dvnce times, lbor requirements, nd other relevnt informtion. Economic nlysis fter three yers showed tht conservtion tillge cn hve economic benefits for growers by reducing input costs, which helps mintin profitble yields Costs nd Returns of Tillge - 3 Yer Averge 14 (2011, 2012, nd 2013) Conventionl Tillge Strip Tillge Minimum Tillge 3 Yr Avg 3 Yr Avg 3 Yr Avg Gross Revenues $/Acre $/Acre $/Acre Returns per Acre $1, $1, $1, Vrible Cost Conv Strip Min Seed $ $ $ Fertilizer $ $ $ Herbicides $36.33 $36.33 $36.33 Insecticides $9.11 $9.11 $9.11 Crop Insurnce $27.67 $27.67 $27.67 Irrigtion Energy $75.00 $75.00 $75.00 nd Lbor* Mchinery Operting $48.00 $21.60 $18.72 Fuel $54.23 $30.26 $25.59 Mchinery Repir $7.00 $3.45 $2.96 Mchinery Lbor $9.00 $4.44 $3.81 Frm Overhed $25.00 $25.00 $25.00 Property Txes $23.67 $23.67 $23.67 Interest (6 months t 8%) $43.88 $39.21 $38.51 Totl Vrible Cost Fixed Costs Mchinery Ownership $ $ $ $48.00 $21.60 $18.72 Totl Fixed Cost $48.00 $21.60 $18.72 Totl Cost $ $ $ Return to Lnd nd Mngement $ $ $ * Estimted from CSU Extension Agriculture & Business Mngement Crop Enterprise Budgets,

17 verged 4% higher under conventionl tillge thn conservtion tillge for corn, soyben, nd winter brley. Property nd equipment costs under conventionl tillge verged nerly 50% higher thn for conservtion tillge. Net return ws slightly higher (2%) for conventionl thn for conservtion tillge when the four crops were considered together in the cropping system. The dt from this study showed similr profitbility for conservtion nd conventionl tillge when ll four crops in this cropping system were considered together. Growers hve found tht using conservtion tillge on their frms provides them with n dditionl $25 to $50 per cre of income. Production costs nd profitbility re highly dependent on individul grower circumstnces. By refining production prctices bsed on grower experience nd the ltest reserch, net returns using conservtion tillge re likely to increse. Reducing input costs by reducing the number of field opertions needed to produce crop while mintining crop yields will promote incresed net grower returns. The Benefits of Using Conservtion Tillge on Furrow-Irrigted Croplnd re: Reduces runoff nd evportion nd increses soil moisture Reduces on nd off-site soil erosion Increses soil orgnic mtter Provides shelter nd hbitt for wildlife Trps snow during winter months Conserves fuel nd lbor by reducing the number of field opertions Sves time due to fewer field opertions Protects wter qulity by reducing surfce wter pollutnts tht my bind to soil prticles, become suspended, nd subsequently crried off the field in tilwter My improve grower bility to ssess perennil weed problems nd identify effective control methods Improves public reltions with the urbn community by using environmentlly sound cropping methods Figure 20. Seedlings emerging from corn residue in no-till field. Photo by Erik Wrdle 15

18 Mking Conservtion Tillge Work Reserch nd experience hve shown tht conservtion tillge cn be used successfully in most cropping systems. In mny situtions, surfce crop residue on furrow-irrigted croplnd cn be mnged without dversely ffecting yields. Furthermore, lrge mounts of surfce crop residue cn be mnged effectively under furrow irrigtion without cusing problems when irrigting, cultivting, or performing other field opertions. Specilized nd specilly-djusted field equipment nd pproprite mngement prctices re necessry for mnging surfce crop residue. Producing crops using conservtion tillge requires growers to be ptient nd cretive in order to be successful t growing nd mnging crops under these conditions. Profitble nd sustinble yields cn be chieve using conservtion tillge, nd significnt svings on fuel, lbor nd input costs mke this n ttrctive opportunity for growers. The environmentl nd wter qulity benefits provide dditionl vlue nd incentives to growers. Reserch projects conducted on both sides of the Continentl Divide in Colordo show compelling evidence tht conservtion tillge cn work under furrow-irrigted systems. As dditionl reserch results re produced nd growers obtin experience with conservtion tillge under furrow irrigtion, more extensive use of this technology is likely to occur. Conservtion tillge under furrow irrigtion my not work in every sitution, but where it does, it mkes good gronomic, environmentl, nd economic sense. Conservtion tillge opens dditionl possibilities, such s the use of living mulch cropping systems. Conservtion Tillge Technology Tht Works Conservtion Tillge Tips There is no one size fits ll system Strt Smll test new equipment nd prctices on limited crege to ensure they will work before strting on the rest of the frm Residue Mngement Size it flil chopping, stright disk (verticl tillge equipment) Move it row cleners Mix it row cleners, ditcher Rotte crops rotte high residue crops with low residue options Strip Till Offset strip till opertion works well leve the root bll in the ground Tke time to get the strip till opertion right sty stright! A crooked strip till opertion will led to chllenges t plnting nd cultivtion nd cuse irrigtion difficulties Fertility Deep injection with the strip till unit followed by strter nd side-dress ppliction works well Brodcst pplictions re not recommended due to lck of incorportion More nitrogen my be needed when inititing conservtion tillge due to nitrogen tie-up cused by the residue Weed Mngement My hve erlier weed pressure nd mngement requirements Volunteer corn cn be chllenge in continuous corn when using Roundup Redy /LibertyLink vrieties Trgeted integrted pest mngement cn help control difficult perennil weeds Irrigtion Flow rtes must be closely monitored nd djusted for conditions very high flow rtes cuse incresed residue dmming, blown out furrows, nd other issues My need to level field before beginning system Be redy to irrigte up (if needed) hving beds nd furrows erly in the seson (before the crop is up) cn reduce issues relted to bedding up with smll plnts in the field 16

19 For more informtion, plese visit conservtiontillge.colostte.edu Selected References Arstd, J.S., nd D.E. Miller Corn residue mngement to reduce erosion in irrigtion furrows. Journl of Soil nd Wter Conservtion 33: Arstd, J.S., nd D.E. Miller Effects of smll mounts of residue on furrow erosion. Soil Science Society of Americ Journl 45: Ashrf, M., C.H. Person, D.G. Westfll, nd R. Shrp Effect of conservtion tillge on crop yields, soil erosion, nd soil properties under furrow irrigtion in western Colordo. Americn Journl of Alterntive Agriculture 14: Berg, R.D Strw residue to control furrow erosion on sloping, irrigted croplnd. Journl of Soil nd Wter Conservtion 39: Bjorneberg, D.T., Westermnn, D.T., Ase, J.K Nutrient losses in surfce irrigtion runoff. Journl of Soil nd Wter Conservtion. 57(6): Brown, M.J Effect of grin strw nd furrow irrigtion strem size on soil erosion nd infiltrtion. Journl of Soil nd Wter Conservtion 40: Brown, M.J., nd W.D. Kemper Using strw in steep furrows to reduce soil erosion nd increse dry ben yields. Journl of Soil nd Wter Conservtion. 42: Crter, D.L Soil erosion on irrigted lnds. pp In: B.A. Stewrt nd D.R. Nielsen (co-eds.) Irrigtion of griculturl crops. ASA Ser. 30, ASA, CSSA, SSSA, Mdison, WI. Crter, D.L., nd R.D. Berg Crop sequences nd conservtion tillge to control irrigtion furrow erosion nd increse frmer income. Journl of Soil nd Wter Conservtion 46: Crter, D.L., R.D. Berg, nd B.J. Snders Producing no-till cerel or corn following lflf. Journl of Production Agriculture 4: Crter, D.L., R.D. Berg, nd B.J. Snders The effect of furrow irrigtion erosion on crop productivity. Soil Science Society of Americ Journl 49: Crop Enterprise Budgets Deprtment of Agriculturl nd Nturl Resource Economics. Colordo Stte University. Accessed 20AUG2015. Dickey, E.C., D.E. Eisenhuer, nd P.J. Js Tillge influences on erosion during furrow irrigtion. Trnsctions of the Americn Society of Agriculturl Engineers 27: Driscol, J.A Wter Conservtion nd Nutrient, Sediment, nd Herbicide Movement in Furrow-irrigted Tillge Systems. CSU Mster s Thesis, Deprtment of Soil nd Crop Sciences. Gynor, J.D., Findly, W.I Soil nd phosphorus loss from conservtion nd conventionl Tillge in corn production. Journl of Environmentl Qulity 24: Lentz, R.D., Lehrsch, G.A Nutrients in runoff from furrow-irrigted field fter incorporting inorgnic fertilizer or mnure. Journl of Environmentl Qulity. 39: Nielsen, D.C Snow Ctch nd Soil Wter Rechrge in Stnding Sunflower Residue. Journl of Production Agriculture. Volume 11, no.4: Person, C.H., J.P, Hin, R.W. Hmmon, nd H.M. Golus Conservtion-tillge grin drill for furrow-irrigted cropping systems. Agronomy Journl 86: Person, C. H., K.D. Syre, nd P.L. Chpmn Nitrogen mngement under no-tillge in furrow-irrigted crop rottion of corn nd whet in western Colordo. Proceedings of the Gret Plins Soil Fertility Conference 8: Person, C.H. nd R.L. Shrp Double-cropping pinto ben fter winter brley in western Colordo. J. Agriculturl Science nd Technology 4:1-7. Person, C.H., Holcomb, C.A., Cooley, A.W, Murry, J.E Guidelines for Using Conservtion Tillge Under Furrow Irrigtion. Technicl Report TR02-6. Colordo Stte University Agriculturl Experiment Sttion. Person, Clvin H., Krl E. White, nd Aubrey L Brinkworth Surfce residue nd soil clods during furrow irrigtion under simulted conditions. Journl of Sustinble Agriculture 12:5-21. Person, Clvin H., Joe E. Brummer, Andrew T. Behm, nd Neil C. Hnsen Kur Clover Living Mulch for Furrow-Irrigted Corn in the Intermountin West. Agron. J. 106: Wortmnn, C.S., Klein, R.N., Shpiro, C.A Hrvesting Crop Residues. NebGuide G1846. University of Nebrsk Lincoln Extension. Yonts, C.D., J.A. Smith, nd J.E. Bilie Furrow irrigtion performnce in reduced-tillge systems. Trnsctions of the Americn Society of Agriculturl Engineers 34:

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