Effects Of Straw And Biochar Returning On Growth And Yield Formationg Of Cotton Under Different N Fertilizer Application Rate

Straw returning and nitrogen fertilizer application are important cultivation measures in cotton field production in saline soil in China,and have an important impact on cotton growth and yield formation.To make the effects of straw and biochar returning on the accumulation and distribution of cotton biomass and yield formation and related factors under different nitrogen application ratestudied,the theoretical support was provided for the rational selection of cotton straw returning way and nitrogen fertilizer application rate,and then which also provided for high and stable yield and high efficiency cotton production.The experiment was carried out in the Dafeng Basic Seed Farm in Dafeng City of Jiangsu province from 2016 to 2017,using insect-resistant cotton.It took two kinds of straw returning method(full amount of straw returning and biochar returning)and three nitrogen application levels(0,150,300 kg N hm-2,expressed as NO,N150,N300),which aims at studing the effects of straw and biochar returning on cotton growth,biomass allocation and yield formation under different nitrogen application rate.The main results were as follows:1.Effects of straw and biochar returning on cotton leaf area and biomass accumulation and distribution under different nitrogen application rateStraw and biochar returning can both increase the accumulation and maximum accumulation rate of total biomass and reproductive organ biomass of cotton plants.With the increase of nitrogen application rate,the accumulation of total biomass and reproductive organ biomass and its maximum accumulation rate showed an increasing trend.Under the same nitrogen application rate,biochar returning was better than straw.The reproductive biomass ratio is higher than N300.Straw and biochar returning increased cotton leaf area index.In the same returning method,the higher the nitrogen application rate,the higher the leaf area index.When the same amount of nitrogen fertilizer was applied,the leaf area index of biochar returning was higher than that of straw in the middle and early stages,especially in 2017.2.Effect of straw and biochar returning on cotton yield formation and related factors under different nitrogen application rateStraw returning and biochar returning significantly increased the number of fruit branches,sites and bolls,and reduced the abscission rate.Biochar returning was more effective in reducing abscission rate.With the increase of nitrogen application rate,the number of cotton branches and sites showed an increasing trend.In bolls number,N150>N300 and it was higher than that of NO treatment.The abscission rate was generally N300>N0>N150.The treatment of straw and biochar returning significantly increased the number of bolls,boll weight and seed cotton yield.The interannual performances of the two returning methods were not consistent.With the increase of nitrogen application rate,the boll number showed an increasing trend,while the boll weight and seed cotton yield were higher in NO than N150 and N300 treatments,and the basic performance between the two was higher than N300,especially in 2017.The contribution of cotton yield components to cotton is represented by the number of bolls>boll weight.The soil moisture content,soil ammonium nitrogen,nitrate nitrogen and available nitrogen content were increased by the two ways of returning,and the ammonium nitrogen and available nitrogen increased with the increase of nitrogen application.