Effect Of Pendimethalin On Weed Control And Nutrient Absorption Of Cotton Under Drip Irrigation In The South Of Xinjiang

Weeds in cotton fields compete for water,nutrient and space with cotton,and this is one of the main factors affecting cotton production.Xinjiang is the major cotton producing areas in our country,has its unique planting patterns.It has the high degree of mechanization,scale on the production management,and the dependence of chemical weed control technology.At present,weeds control in cotton fields mainly depend on spraying herbicide on the soil surface before sowing of seeds in the South of Xinjiang,and a manual weeding would still need at middle-late growing stages.It raises the labor cost of cotton plantation.Aiming at the technology application of integrated management of water,fertilizer and pesticide for weeds control in cotton fields,this study uses cotton and pendimethalin as testing materials.Fields experiment were performed to study different pendimethalin application methods on weed control effect and its influence on cotton,weed nutrient absorption under drip irrigation in the South of Xinjiang.The main conclusions are presented as follows:(1) Spraying pendimethalin on the soil surface before sowing of seeds and application of integrated managemen of water, pendimethalin at the first drip irrigation treatment significantly decreased the dry weight of weeds,reducing the number of weeds.Spraying herbicide on the soil surface before sowing of seeds treatment of the total grass average control efficiency greater than 80% at 33 d after application,after the application of 55 d the soil surface before sowing of seeds on weed control effect is higher than that of 33 d after application;application of integrated managemen of water,pendimethalin at the first drip irrigation treatment after application 15 d and 30 d weed control efficiency were significantly higher than that of non application of integrated managemen of water, pendimethalin at the first drip irrigation applicated treatments.(2) Spraying pendimethalin on the soil surface before sowing of seeds compared with non spraying pendimethalin on the soil surface before sowing of seeds treatment of weeds N,P,K content had no significant effect,but significantly reduces the nutrient uptake of weeds after the cotton emergence 23 d(seedling stage),51 d(bud stag),71 d(flowering stage).Application of integrated managemen of water,pendimethalin at the first drip irrigation applicated treatment compared with non application of integrated managemen of water,pendimethalin at the first drip irrigation treatment weeds N,P,K nutrient content and nutrient uptake decreased after the cotton emergence93 d(boll stage),121 d,144 d(boll opening).Spraying herbicide on the soil surface before sowing of seeds than spraying herbicide on the soil surface before sowing of seeds treatment Chenopodium glaucum N,P,K nutrient uptake decreased by 78.6%,75%,52%after the cotton emergence 71 d(flowering stage);application of integrated managemen of water,pendimethalin at the first drip irrigation applicated treatment compared with non application of integrated managemen of water, pendimethalin at the first drip irrigation treatment Chenopodium glaucum N,P,K nutrient content respectively decreased by 27%,15%,N,P,K respectively decreased by 45%,59%,45% after the cotton emergence 121 d.(3) Pendimethalin applied spraying herbicide on the soil surface before sowing of seeds treatment of cotton plant height, stem diameter, number of stem sections were increased by 13%,9% and 15% after cotton emergence 69 d(bud stag).Cotton emergence after 93 d(boll stage) of stem diameter spraying pendimethalin on the soil surface before sowing of seeds + application of integrated managemen of water,pendimethalin at the first drip irrigation treatment less non spraying pendimethalin on the soil surfacebefore sowing of seeds + non application of integrated managemen of water,pendimethalin at the first drip irrigation treatment increased by 8%,the bud number of spraying pendimethalin on the soil surface before sowing of seeds + application of integrated managemen of water, pendimethalin at the first drip irrigation treatment less non spraying pendimethalin on the soil surface before sowing of seeds + non application of integrated managemen of water,pendimethalin at the first drip irrigation treatment increased by 22%.(4) Applied spraying pendimethalin on the soil surface before sowing of seeds treatment of cotton dry matter accumulation significantly higher than non applied spraying pendimethalin on the soil surface before sowing of seeds treatment after the cotton emergence 51 d(bud stag),71 d(flowering stage),application of integrated managemen of water, pendimethalin at the first drip irrigation of cotton dry matter accumulation also significantly higher than non application of integrated managemen of water,pendimethalin at the first drip irrigation treatment after the cotton emergence 93 d(boll stage),121 d,144d(boll opening).Spraying herbicide on the soil surface before sowing of seeds treatment plant dry weight than unclosed applicated treatment increased by 36% after the cotton emergence 51 d(bud stag),application of integrated managemen of water, pendimethalin at the first drip irrigation than non application of integrated managemen of water, pendimethalin at the first drip irrigation treatment seed cotton and plant dry weight respectively increased by 42%,12% after the cotton emergence 121 d.(5) Applied spraying pendimethalin on the soil surface before sowing of seeds will be decreased cotton N,K nutrient content,and have no significant effect on the nutrient content of P,application of integrated managemen of water, pendimethalin at the first drip irrigation treatment reduced the cotton N,P,K nutrient content,but still significantly increased nutrient uptake.Closed before sowing than unclosed treatment plant N content reduced by 5% after the cotton emergence 51 d(bud stag),K content reduced by 13% after the cotton emergence 71 d(flowering stage);application of integrated managemen of water, pendimethalin at the first drip irrigation than non application of integrated managemen of water, pendimethalin at the first drip irrigation treatment total plant N,P,K nutrient content decreased by 12%,10%,16%,plant N,P,K nutrient uptake decreased by 32%,19%,15% after the cotton emergence 121 d.(6) Applied spraying pendimethalin on the soil surface before sowing of seeds and application of integrated managemen of water, pendimethalin at the first drip irrigation treatment is an effective way of prevention and control of weeds in cotton fields in the south of Xinjiang.