Effects Of Nitrogen Reduction Combined With Biochar On Soil Organic Carbon,Nitrogen Utilization And Yield Of Spring Wheat

In order to explore the effects of combined application of biochar soil organic carbon content,nitrogen absorption and utilization of spring wheat and yield in Northern Xinjiang irrigation area under the condition of chemical nitrogen fertilizer reduction,eight treatments were set up: control(no nitrogen application,CK),conventional nitrogen application(300kg·hm-2,N1),biochar only(20 t·hm-2,B),conventional nitrogen application + biochar(N1B),nitrogen reduction by 15%(255 kg·hm-2,N2),nitrogen reduction by 15% + biochar(N2B),nitrogen reduction by 30%(210 kg·hm-2,N3),nitrogen reduction by 30% + biochar(N3B),The effects of different treatments on spring wheat yield formation,plant nitrogen absorption and utilization,wheat field soil respiration and organic carbon content were studied,and the appropriate combined application amount of nitrogen fertilizer and biochar was selected,It provides a theoretical basis for the agricultural production and utilization of biochar and the development of low-carbon agriculture in Northern Xinjiang.The main results are as follows:(1)The addition of biochar can significantly reduce soil respiration and bulk density and increase the content of organic carbon.Compared with no fertilization and single application of nitrogen fertilizer,the total organic carbon(SOC),active organic carbon(AOC),carbon pool management index(CPMI)and yield of soil increased after application of biochar,while the soil respiration rate decreased,and the soil respiration rate and bulk density of single application of biochar were the lowest.The content of SOC in N3 B treatment was the highest,which was27.93 g·kg-1;The content of AOC reached the maximum in N2 B treatment,which was 1.47g·kg-1,which was about 4.72% and 25.17% higher than that of conventional nitrogen application N1.(2)Under the condition of reduced nitrogen application,the nitrogen absorption and utilization efficiency of spring wheat increased,and reached a significant level after combined application of biochar.The nitrogen utilization efficiency was the highest under N2 B treatment,and the nitrogen absorption efficiency reached the highest under N3 B treatment,which was significantly increased by about 68.23% and 74.17% respectively compared with conventional nitrogen application N1;The agronomic utilization rate of nitrogen fertilizer showed a downward trend with the decrease of nitrogen application.Under the condition of nitrogen reduction,it increased significantly after combined application of biochar,and reached the maximum in N2 B treatment,which was 12.40,which was significantly increased by about55.40% compared with conventional nitrogen application N1.(3)Compared with conventional nitrogen application,simple nitrogen reduction(N2,N3)had no significant effect on photosynthesis,material accumulation and transportation of spring wheat,but the yield and its constituent elements and agronomic utilization efficiency of nitrogen fertilizer decreased with the decrease of nitrogen application,and the above indexes were significantly improved after combined application of biochar.In the comprehensive performance,the effect of 15% nitrogen reduction combined with biochar treatment(N2B)was the best.Under this treatment,the SPAD value and net photosynthetic rate of flag leaves were at a high level.The dry weight of single stem at maturity,the proportion of grains to single stem weight,the contribution rate of pre flowering assimilates to grains were 5.01 g·plant-1,51.31%and 18.03% respectively.The grain yield was 8301.35 kg·hm-2,which increased by about 38.09%and 18.11% compared with CK and conventional nitrogen application.