Study On The Methane Emission From Paddy Soil After The Change Of Long-term Fertilization Management

In this study, three red paddy soils have been cultivated under different organic fertilization treatments in a 30 years fertilizer experiment in Hunan Agricultural University. The soil organic carbon content of red paddy soils,which reported to be steady after 30 years’ cultivation,was adjusted to the following seven treatments without compromising the original experiment:the chemical fertilization treatment changed from normal organic fertilization treatment(N-C),the chemical fertilization treatment changed from high organic fertilization treatment(H-C), the normal organic fertilization treatment changed from chemical fertilization (C-N),the original normal organic fertilization treatment(NOM),the high organic fertilization treatment changed from the original normal organic fertilization treatment(N-H),the original high organic fertilization treatment(HOM), the original chemical fertilization treatment(CF). CH4 flux of the seven treatments was measured to study the effects of the following-up fertilization reforming on the CH4 flux in red paddy soils with different fertilities and soil organic carbon (SOC) from 2012 to 2014. The results showed that the CH4 flux in the soils under long-term organic fertilization treatments decreased after the adjustment from organic fertilization to chemical fertilization. However, the CH4 flux in the soils under long-term chemical fertilization treatments increased remarkably after the adjustment from chemical fertilization to organic fertilization. The organic fertilization had obvious impacts on the dynamics of CH4 flux.The organic fertilization (x) had a significantly positive relationship with the total amount of annual CH4 (y) (y=0.1677x+2.746, R2=0.9642, n=21). CH4 flux also had a positive relationship with the increasing of SOC. Annual dynamics of CH4 flux in different fertilization paddy soils had significant correlation with SOC. Under same organic fertilization treatment or chemical fertilization, CH4 flux with high SOC content was larger than that in the soils with low SOC content. The inherent SOC content (x) had a positive relationship with the total amount of annual CH4 (y) (y=0.5154x-4.3454, R2=0.932, n=9) in the paddy soils received chemical fertilization. Organic fertilization can promote decomposition of soil organic carbon and emission of CH4.Comepared with the constants of organic fertiliztion in a given amount of organic carbon content,the decomposition rate of high amount of organic fertiliztion is 1.52% higher.In same amount of organic fertiliztion but different soil organic carbon content, soil organic carbon decomposition ratio have no significant difference. Similarly.the soil organic carbon also can promote decomposition of organic material carbon and releasing CH4.In constant organic fertiliztion or high amount of organic fertiliztion treatment, Comparing higher soil organic carbon content to the lower, carbon decomposition ratio of organic material is more than 3.29% and 2.52% respectively.