(93%) cotton nd percent lint ws similr in oth pickers. The 15-inch row system with 27 plnts/a gve higher lint yield (1491 l/a) compred to 4-inch row cotton with 5 plnts/a (136 l/a). Plnt cnopy closed 3 weeks erlier in twin-row cotton nd 4 weeks erlier in 15inch row cotton thn in 4-inch row cotton with potentil to eliminte t lest one Roundup postemergence ppliction. Results of this one yer study indicte tht 15-inch row nd twin-row plnting systems using equl or less plnt popultions s tht of 4-inch row system could produce lint yield equl or higher thn 4-inch row system under oth irrigted nd non-irrigted conditions. It should e stressed tht in 15-inch row system, lint yield ws corrected for 8% of lnd re s 2 of 1 rows were skipped under tire trcks. Lint yields will increse s the numer of rows plnted per trip increse, for exmple, correction fctor will e 9% for 2 of 2 nd 93% for 2 of 3 rows skipped. Presently, no picker is ville to hrvest cotton in 1-inch twin-row system. However, if n djustle row picker ecomes ville, twin-row of 15-inch prt on 4- inch center is possiility. Conservtion Tillge Strtegies or Corn, Sorghum And Cotton Presented y Chrles Stichler Agronomist, Stichler Agriculture Services Conservtion nd reduced tillge continues to chnge nd dpttions mde to mtch the conditions of ech producer nd the prolems encountered. With the shift in weeds nd hericide resistnt io-types eginning to pper in fields, producers must e wre nd mke hrd choices. Rotting hericides nd using comintions to kill dpting weeds, will ecome more importnt if producers wnt to continue using reduces tillge s vile option. Some limited tillge my e necessry to reduce the dependence on hericides. ertilizer plcement nd compction re lso issues over long period. Although crop roots re le to pick up nutrients from smll nd it will e importnt to move the nd to different res ner the plnted row. Crops with lrge root systems such s corn often respond when roots throughout the soil hve ccess to nutrients. Stle seed eds in higher rinfll res nd strip tillge in other res re predomintely the most successful reduced tillge prctices. Permnent equipment ptterns, killing sorghum efore hrvest when possile nd cotton s soon s possile fter hrvest continue to e importnt mngement prctices. ormuls work for ded things ut not for living orgnisms. rming is living in the sense tht ech yer, seson nd crop with its chllenges re different. Conservtion Vs Conventionl Tillge, Doule Cropping And Cover Crop Effects On Crop Production And Wter Use In Sutropicl South Texs Presented y Dr. Bo Wiedenfeld Professor of Soil Science, Texs Ag. Experiment Sttion Wter vilility for irrigtion hs ecome mjor concern for South Texs. Conservtion tillge offers the dvntge of reduced field opertions compred to conventionl tillge which should result in lower costs, etter yields nd reduced risk. Wter loss is reduced, soil structure improves, nd oxidtion of orgnic residues is not s rpid s tillge is reduced. Hopefully this will result more efficient wter use s well s lower costs. Wter svings due to reduced tillge, however, hve thus fr not een reported. Doule cropping nd cover crops offer the potentil to increse orgnic mtter ccumultion improving soil properties, ut will increse initil wter requirements. Plnting nd weed control re mjor chllenges for implementing conservtion tillge. The ojective of this study is to compre conservtion vs conventionl tillge, nd lso to evlute fll doule cropping nd cool seson cover crops compred to fll fllow under conservtion tillge. Pge 2 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book
Mterils & Methods A study is eing conducted in Lower Rio Grnde Vlley of Texs, n re with climte tht is sutropicl (verge dily temperture rnges from high of 84 o in July to low of 6 o in Jnury), nd semirid (verge nnul rinfll < 24 in.). A innul cotton sorghum rottion is eing grown, nd four cropping tretments re eing pplied: 1) conventionl tillge - fll fllow; 2) conservtion tillge - fll fllow; 3) conservtion tillge - fll doule crop; 4) conservtion tillge - fll cover crop. The doule crops re corn following cotton, nd soyen following sorghum; nd the cover crops re lck ots following cotton, nd hiry vetch following sorghum. Spring crops re eing furrow irrigted s required, nd fll crops re eing grown for the most prt without irrigtion. The study ws initited in the fll of 22 nd is currently in the 4 th spring crop, which will e the completion of the 2-yer rottion for the 2nd time. Conventionl tillge consists of shredding following crop hrvest, disking severl times, deep chisseling in 2 directions, disking severl times gin, then edding up the lnd. The field is cultivted s required to control ny weeds until the next crop is plnted, nd s the crop is grown. Conservtion tillge ttempts to leve previous crop residues on the soil surfce s long s possile, nd to reduce tillge opertions. Cultivtion is typiclly performed prior to ny furrow irrigtion in order to mintin rised eds to fcilitte furrow irrigtion. Weed control is performed using hericides. Prmeters eing mesured include vrious crop responses, irrigtion requirements nd chnges in soil properties. Results & Discussion The primry differences in soil wter use etween the tillge & cropping tretments in this study occurred during the fllow periods due to differences in the cover tht ws left on the soil surfce, nd in the fll due to differences in wter use y the crop eing grown (ig. 1). Wter use y the spring crops ws ffected only slightly y tillge nd soil cover, cotton using etween 3.6 nd 32.4 inches nd sorghum using etween 17.6 nd 18.5 inches of wter. Wter loss during the fllow periods ws reduced 25% y the retention of crop residue on the surfce. Where no fll crop ws grown, conservtion tillge resulted in n verge 11.5% reduction in wter use compred to conventionl tillge. The fll cover crops used n verge 11.3 inches of dditionl wter, ut over hlf of tht ws recovered through svings from the reduced wter loss due to the surfce residue. ll doule crops use n dditionl 15 to 24 inches of wter. Only out third of this is recovered y reduced losses due to the crop residues. These differences re reflected in the mount of irrigtion wter required to furrow irrigte the cropping tretments the following spring (ig. 2). Crop yield responses to the tillge systems vried etween yers. In 23 grin sorghum yields showed only slight tretment differences (ig. 3). Cotton in 24 (ig. 4) nd grin sorghum in 25 (ig. 3) oth hd lower yields where fll doule crop or winter cover crop hd een grown the previous yer compred to fll fllow. In 26 cotton yields were not ffected y tillge tretment (ig. 4). No yield differences hve een found etween conventionl nd conservtion tillge where the soil ws left fllow the previous fll. Although not lwys consistent, soil NO3 --N levels mesured in Jnury were highest for fll fllow (conservtion nd conventionl tillge) compred to fll doule cropping nd cover crops most yers, which my reflect immoiliztion of soil N y the fll crop (ig. 5). Orgnic mtter contents rose from.8% t the initition of this study to 1.21% fter the first yer, ut hs remined constnt therefter (ig. 6), nd hs shown no sttisticlly significnt differences due to the tillge tretments pplied. Other studies hve reported increses in orgnic C prticulrly ner the surfce t some point in time under no-till, ut no increse in orgnic mtter levels hve een reported for ny reduced tillge system tht involves t lest some tillge. Conclusions Conservtion tillge in sutropicl South Texs offers dvntges over conventionl tillge, ut lso poses significnt chllenges. New procedures nd equipment modifictions re required. Plnting nd weed control re difficult. Wter svings re errtic depending on rinfll pttern, ut improved soil moisture sttus t ny given time would improve the chnges of mking crop when drought conditions occur. Differences in soil wter sttus so fr hve een due only to crop nd surfce residues, nd not due to ny long term chnges in soil properties. Crop yields re the sme etween conservtion & conventionl tillge, ut cn e reduced y fll doule cropping nd winter cover crops. Sustntilly lower costs, however, due to fewer field opertions would e definite enefit of conservtion tillge. Pge 21 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book
.4 Dily Crop Wter Use wter use (in./dy).3.2.1. Jn e Mr Apr My Jun Jul Aug Sep Oct Nov Dec dte Conventionl, ll - fllow Con till, ll - fllow Con till - ll - ots Con till - ll - corn igure 1. Dily crop wter use sed on ET for spring cotton followed y fll fllow, ots or corn. urrow Irrigtion 1 8 3 Mr 1 My 6 inches 4 2 conventionl conservtion conservtion conservtion fll fllow fll fllow fll cover crop fll doule crop igure 2. Amount of irrigtion wter pplied on 2 dtes. Notes: Pge 22 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book
S orghum Yie ld ls/c 25 2 15 1 1 - conventionl / fll fllow 2 - con till / fll fllow 3 - con till / fll cover crop 4 - con till / fll doule crop 5 1 2 3 4 1 2 3 4 23 25 igure 3. Grin sorghum yields. Cotton Lint Yield 16 14 12 1 - con ventionl / fll fllow 2 - con till / fll fllow 3 - con till / fll cover crop 4 - con till / fll doule crop 1 ls/c 8 6 4 2 1 2 3 4 1 2 3 4 24 26 igure 4. Cotton yields. Pge 23 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book Pge 23 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book
35 3 25 Soil NO 3 -N 1 - c onv entionl / fll fllow 2 - con till / fll fllow 3 - con till / fll cov er crop 4 - con t ill / fll doule crop ppm 2 15 1 5 1 2 3 4 1 2 3 4 1 2 3 4 1.4 Orgnic Mtter Content 1.2 1. % 23 25 26 igure 5. Soil NO3 igure -N during 5. winter Soil prior NOto 3 Nplnting during spring winter crops. prior to plnting s i.8.6.4 22 23 24 25 26 Yer igure 6. Soil orgnic mtter content during winter prior to plnting spring crops. Pge 24 Tenth Annul Ntionl Conservtion Systems Cotton & Rice Conference Proceedings Book