Effects Of Biochar And Humic Acid On Yield,nutrient Absorption And Loss Risk Of Double Cropping Rice In Dongting Lake

In order to reduce the amount of fertilizer rate of double cropping rice in dongting lake plain,and achieve green cultivation of double cropping rice,field experiment with eight treatments,which was only application of potassium fertilizer（T₁）,conventional fertilization（T₂）,reduction of nitrogen and phosphorus by 20%（T₃）,reduction of nitrogen and phosphorus by 20%+humic acid（T₄）,reduction of nitrogen and phosphorus by 20%+biochar ₁（T₅）,reduction of nitrogen and phosphorus by 20%+biochar₂（T₆）,reduction of nitrogen and phosphorus by 20%+humic acid+biochar ₁（T₇）,reduction of nitrogen and phosphorus by 20%+humic acid+biochar ₂（T₈）were set up in this paper to study the effects of 20%reduction of nitrogen and phosphorus with application of humic acid and biochar on rice yield,nutrient absorption and loss of nitrogen and phosphorus.The results would provide scientific basis for the green cultivation of rice in double cropping rice area of dongting lake plain.The research results are as follows:1,The reduction of nitrogen and phosphorus by 20%and adding application of biochar and humic acid had no significant effect on the panicle length,effective panicle number per stump and 1000-grain weight of double-cropping rice.However,combined application of biochar and humic acid on the basis of 20%reduction of nitrogen and phosphorus could significantly increase plant height,grain number and grain yield of double-cropping rice.Adding biochar（4500kg/hm²）or adding biochar and humic acid at the same time on the basis of 20%reduction of nitrogen and phosphorus could significantly increase the setting rate of double-cropping rice.The reduction of nitrogen and phosphorus by 20%and adding application of biochar and humic acid had no significant effect on nitrogen,phosphorus and potassium content in rice grains and straws at the harvest stage,but it significantly improved the nitrogen utilization rate of double-cropping rice.Combined application of biochar and humic acid on the basis of 20%reduction of nitrogen and phosphorus can significantly improve phosphorus use efficiency and partial productivity of nitrogen fertilizer;combined application of biochar（2250kg/hm²）or combined application of biochar and humic acid on the basis of 20%reduction of nitrogen and phosphorus can significantly improve agronomic utilization rate of early rice.2,Compared with the conventional fertilization treatment,reduction of nitrogen and phosphate by 20%,can significantly reduce the concentration of soluble nitrogen,total nitrogen,ammonium nitrogen,nitrate nitrogen,total phosphorus and soluble phosphorus in the the cropping field surface water.The addition of biochar makes the treatment effect better,and the reduction of 20%at the same time with biochar and humic acid treatment effect is best.The concentration of total N and total P were reduced by 16.21%-32.93and 16.41%-30.97%respectively in the reduction of nitrogen and phosphorus by 20%and adding application of biochar and humic acid treatments compared with the conventional fertilization treatment.Compared with reduction of nitrogen and phosphorus by 20%treatment,the concentration of total N and total P were reduced by 3.18%-17.72%and 3.23%-15.89%respectively in the reduction of nitrogen and phosphorus by 20%and adding application of biochar and humic acid treatments.3,The treatment of deducting nitrogen and phosphorus by 20%with adding application of biochar and humic acid,which was T₇and T₈,were considered as the best fertilization pattern because of the highest yield and least loss of nitrogen and phosphorus.however,considering that the yield difference between T7and T8 was not significant,T7 was the suitable fertilization pattern because of its lower cost.Under this way of fertilization,compared with the treatment of 20%reduction of nitrogen and phosphate,the concentrations of total nitrogen,soluble nitrogen,ammonium nitrogen,nitrate nitrogen,total phosphorus and soluble phosphorus in the field surface water of early rice were decreased by 16.35%,13.45%,17.39%,14.06%,13.21%and 13.95%,respectively;and decreased by 10.51%,10.78%,9.43%,16.90%,12.90%,13.33%respectively in the surface water of late rice field.4,The application of biochar and humic acid on the basis of 20%reduction of nitrogen and phosphate significantly improved the available potassium content in soils,And the available potassium content was increased with the raised amount application of biochar.The application of humic acid on the basis of 20%reduction of nitrogen and phosphate significantly increased the available phosphorus content in soils,While application of biochar on the basis of 20%reduction of nitrogen and phosphorus had no significant effect on the available phosphorus content.The application of biochar（2250 kg/hm²）and humic acid on the basis of 20%reduction of nitrogen and phosphate significantly improved the content of alkali-hydrolyzed nitrogen in the soils.However the content of alkali-hydrolyzed nitrogen in the soils at the harvest stage could be significantly reduced under the condition of high dosage of biochar application.