Effects Of Biochar Managements Methods On Growth And Nitrogen Utilization Of Rice Under The Wet-dry Cycling Irrigation

Rice is one of the main food crops in China and one of the most water-intensive crops.The relative shortage of water resources and the low utilization rate of nitrogen fertilizer have turn into important factors that restrict sustainable development of rice in China and affect virtuous cycle of ecological environment.It is of significance to vigorously promote the green and efficient water application of rice.Therefore,in this study,biochar was applied to the rice production system.Using split-plot field experiment design,the nitrogen application rate in the main area was set at four levels(N₀,0 kg·ha^-1;N₁,70 kg·ha^-1;N₂,140 kg·ha^-1;N₃,210kg·ha^-1),two levels of biochar in the sub-area(B₀,0 t·ha^-1;B₁,10 t·ha^-1),studied the different nitrogen application rates and biochar and their interaction The effect of the effect on rice growth and yield,the mechanism of biochar on rice yield increase and nitrogen accumulation;on this basis,using split-plot pot experiment,the main area irrigation mode includes conventional irrigation（W₀）and wet and dry Alternate irrigation（W₁）two levels,sub-area biochar management including no biochar（B₀）、10 t·ha^-1biochar mixed application(B_1m)、10 t·ha^-1biochar surface application(B_1s)、20 t·ha^-1biochar mixed application(B_2m)、20t·ha^-1biochar surface application(B_2s)five levels,analysis of two irrigation modes and five biochar management methods and their interaction effects Irrigation methods and organisms were proposed for rice growth,physiological characteristics,nitrogen accumulation,water use efficiency,yield and yield components,propose the best combination of irrigation and biochar management methods,in order to provide theoretical basis for efficient water and fertilizer management of northern rice.The main results are as follows:（1）Nitrogen application rate and biochar main effect on growth index（including tiller number and leaf area index）,physiological index（chlorophyll content and net photosynthetic rate）of rice,dry matter accumulation and nitrogen accumulation in all organs Significantly,the N₃and B₁ levels were most effective.Compared with N₀ level rice production,N₃ levels increased significantly by 2 times（2015）and 1.4 times（2016）.The biochar The biochar(10t·ha^-1)rice yielding effect is obvious,B₁（8.04a）>B₀（7.50b）（2015）;B₁（7.20a）>B₀（6.83b）（2016）and the organism.（2）Under the condition of conventional nitrogen application(210 kg·ha^-1),the addition of biochar(10 t·ha^-1)in paddy field can significantly increase chlorophyll content,net photosynthetic rate and leaf area index,and promote dry matter of rice.accumulation.The dry matter accumulation and nitrogen accumulation in the shoots of N₃B₁ treated rice increased by 6.1%and 13.4%,respectively,compared with N₃B₀ treatment（2016）.N₃B₁treatment had the highest yield of rice,and N₃B₁ treatment increased yield by 18.3%（2015）and 13.3%（2016）compared with N₃B₀ treatment.（3）Dry and wet alternate irrigation reduced water consumption（8.9%）and increased water use efficiency（7.6%）on the basis of ensuring stable rice production.N₀ significant impact on other indicators.The application of biochar in rice fields can enhance soil water retention capacity.Compared with B₀,B_1m,B_1s,B_2m and B_2s reduce total water consumption during the whole growth period by 11.2%,9.7%,8.9%and 6.8%,and increase water use efficiency by 29.5%.23.7%,18.0%and 14.4%.（4）Under the application of biochar and mixed application,the application of biochar can increase the total nitrogen and ammonium nitrogen in soil,which is needed for providing rice plants.Nitrogen promotes nitrogen uptake by plants,and the effect of biochar is more obvious.（5）Compared with the control,the application of biochar can promote the growth of rice leaves,maintain high leaf area index and chlorophyll content,increase the net photosynthetic rate of rice,and contribute to the accumulation of dry matter in various organs of rice.The dry matter quality of the aboveground parts of B_1m,B_1s,B_2m and B_2s increased by 14.4%,10.8%,6.7%and 5.9%,respectively,compared with B₀.（6）The application of biochar increased the yield of rice under different irrigation methods.The treatment effects of W₀B_1m,W₀B_1s and W₁B_1m were the best,and the yield increase effect was significantly higher than other treatments（P<0.05）,but there was no statistical difference between the three.Compared with W₁B₀,W₁B_1s and W₁B_2m,W₁B_1mtreatment increased yield by 19.2%,2.3%and 4.9%respectively.It can be seen that 10 t·ha^-1biochar effect is better than 20 t·ha^-1 under the conditions of mixed application of dry and wet driving.The effect of mixed application under the condition of consistent use of biochar is better than that of the surface.Compared with W₀B_1m treatment,W₁B_1m treatment reduced production by 3.4%,but total water consumption decreased by 10.2%,and water use efficiency increased by 6.3%.After comprehensive analysis,the optimal stable yield and water-saving treatment recommended in this study is mixed application of l0 t·ha^-1 under alternate dry-wet irrigation Biochar treatment.