Effects Of Long-Term Straw Returned To Soil On Cotton Yield And Nutrient Uptake In The Wheat-cotton Rotation System

The experiment were conducted from 2011 to 2015 in the experiment station of Nanjing and Dafeng in China.application rates of wheat straw in cotton season were designated as 0,4500 and 9000 kg ha-1 and those of cotton residue in wheat season were designated as 0,3750 and 7500 kg ha-1 Finally,there were nine crop residue incorporation treatments without chemical K fertilizer applied in the wheat-cotton rotation system,by the processes of independent assortment of wheat straw and cotton residue.Additionally,two independent K fertilizer treatments without crop residue incorporation were designated as 150 and 300 kg K2O ha-1(K150 and K300),with potassium sulfate(50%K2O)applied as basal fertilizer in cotton season,and they were not applied in wheat season.This study was conducted to monitor crop yield,biomass,nutrient uptake in 2014-2015,combining with the results of previous studies,analyse the effect of long-term K fertilizer application and returning wheat straw to soil on crop yield.The main results were as follows:1.Effects of long-term straw returned to soil on cotton yield in the wheat-cotton rotation systemIn 2014 and 2015,straw returning can increased boll number and seedcotton yield,the yield increasing was effected by different straw returning rate.the yield increasing and the chemical K replacement rates by wheat straw decreased with the numbers of years of wheat straw returning.2.Effects of long-term straw returned to soil on cotton biomass in the wheat-cotton rotation systemStraw returning can increased fruiting branch,fruiting sites,reduced the abscission rate in 2014 and 2015.Applying potash and wheat straw increased the biomass accumulation of cotton,Wheat straw and potash fertilizer increased biomass of cotton reproductive organs,reducing the proportion of reproductive organs,effectively alleviate the premature aging of cotton.3.Effects of long-term straw returned to soil on cotton nutrients uptake in the wheat-cotton rotation systemNitrogen,phosphorus concentration in cotton increased by the straw returning and K application in 2014 and 2015.The potassium uptake was larger than phosphorus uptake by cotton.The uptake of nitrogen?phosphorus?potassium of W9000(9000 kg ha-1)was larger than that of W4500(4500 kg ha-1).The uptake of nitrogen?phosphorus?potassium by potassium application was larger than by wheat straw.Overall,straw returning increased the seedcotton yield?nitrogen and phosphorus concentration in 2014 and 2015.The chemical K replacement rates by wheat straw decreased with the numbers of years of wheat straw returning.