Study On Fertilizer And Water Management Technology For Ammonia Volatilization Emission Reduction In Paddy Fields

Ammonia（NH₃）volatilization is one of the important ways of nitrogen loss in paddy fields,which not only reduces the utilization efficiency of nitrogen fertilizer,but also causes ecological and environmental problems such as increased atmospheric PM_2.5 particles and nitrogen dry and wet deposition.The blind pursuit of high rice yield and high fertilizer-tolerant varieties has led to high cropland replanting index and excessive nitrogen fertilizer inputs,and ammonia volatilization is extremely prominent.Currently,there have been many studies on emission reduction measures for ammonia volatilization in southern double-cropping paddy fields,but single measures have problems such as limited emission reduction effect and low economic benefits.Therefore,how to reduce ammonia volatilization losses effectively and practically through the integration of scientific fertilizer and water management technology is the focus of current research in agricultural environment.In this thesis,we used indoor incubation test to screen out slow-release urea from（coated urea,loss-controlled urea,carbon-based fertilizer,silica-containing urea and synergistic fertilizer）,and then combining with field plot test to further study the effect of 16.7%reduction of nitrogen fertilizer,deep application,straw returning and deep flooding during fertilization period on ammonia volatilization.An efficient and practical ammonia volatilization and emission reduction technology model of coated urea reduction and deep application+straw returning+deep flooding was constructed.The main results are as follows:1.Coated urea（PU）had the best control effect on ammonia volatilization,followed by loss-controlled urea（LU）,both of which had low ammonia volatilization from 1 to 17 days after fertilization,mainly due to the reduction of ammonium nitrogen（NH₄⁺-N）concentration in the surface water.2.Single technologies such as slow-release urea reduction（PU₁ and LU₁）,deep application,straw returning（R₁）and deep flooding during fertilization period（W₁）were beneficial in reducing ammonia volatilization.Conventional urea deep application（CU）reduced annual ammonia volatilization by 15.3%～21.6%（P<0.05）compared to surface application（CF）.PU₁ and LU₁ reduction deep application reduced annual ammonia volatilization by 75.6%and 39.1%（P<0.05）compared to CU.PU₁ reduction reduced annual ammonia volatilization by 20.5%（P<0.05）compared to PU regular deep application.Straw returning（R₁）reduced annual ammonia volatilization by 8.6%～14.2%compared with straw removal（R₀）.Compared with conventional water management（W₀）,deep flooding（W₁）reduced field water NH₄⁺-N concentration by 7.7%and 15.2%for early and late rice fertilization periods（1～5 day）,and total ammonia volatilization was reduced by11.2%and 20.7%,respectively.3.The integrated coated urea reduction deep fertilization（PU₁）+straw returning（R₁）or deep flooding（W₁）had the best effect on reducing ammonia volatilization.Compared with conventional urea surface application（CF）treatment,the annual total ammonia volatilization loss（rate）was 97.1～103.1 kg·N·hm^-2（26.2%～28.7%）,the total ammonia volatilization of early and late rice treated with PU₁R₁ in 2019 can be reduced by 78.9%and 83.6%respectively（P<0.05）,and treated with PU₁R₁W₁ in 2020 can be reduced by 74.5%and 87.4%respectively（P<0.05）.The correlation analysis between ammonia volatilization and influencing factors showed that the total nitrogen（TN）and NH₄⁺-N concentrations in the field surface water were positively correlated with the NH₃ volatilization flux/accumulation,and the NH₃ volatilization accumulation was extremely significantly positively correlated（P<0.01）,the correlation coefficient is as high as 0.90.4.Fertilizer and water management measures with better ammonia volatilization emission reduction effect can also improve nitrogen use efficiency and yield of rice.Compared with CU,PU₁ increased the partial productivity of nitrogen fertilizer by 21.5%～22.2%（P<0.05）for early and late rice,and achieved an annual yield increase of 2.1%.Compared with R₀,R₁ improved the nitrogen use efficiency of rice and the content of soil nutrients,in which the content of soil total nitrogen increased by 2.8%～5.9%,and achieved an annual yield increase of3.2%～8.5%.W₁ had almost no effect on rice nitrogen use efficiency,yield and content of soil nutrients compared with W₀.Compared with the CF treatment,PU₁R₁W₁ treatment with integrated emission reduction technology reduced the apparent annual nitrogen loss by 35.6%（P<0.05）,greatly improved the nitrogen use efficiency of rice and content of soil nutrients,and achieved an annual yield increase of 16.8%（P<0.05）,while the economic and environmental benefits increased by927.6 yuan·hm^-2 and 363.6 yuan·hm^-2,respectively,and the comprehensive economic and environmental benefits increased by 1291.6 yuan·hm^-2 annually.