改变施肥管理后不同肥力稻田土壤CO2的排放特征

Abstract

Paddy soils show significant potential of carbon sequestration. The soil organic carbon( SOC) content of red paddy soils have been reported to be steady after 30 years' cultivation and it varies with different fertilization practice. In this study,three red paddy soils,which cultivated under different organic fertilization treatments in a 30 years fertilizer experiment in Changsha, China, was adjusted to the following seven treatments without compromising the original experiment: the original high organic fertilization treatment( HOM),the high organic fertilization treatment changed from the original normal organic fertilization treatment( N-H),the original normal organic fertilization treatment( NOM),the normal organic fertilization treatment changed from chemical fertilization( C-N),the chemical fertilization treatment changed from high organic fertilization treatment( H-C),the chemical fertilization treatment changed from normal organic fertilization treatment( N-C),the original chemical fertilization treatment( CF). CO2 flux of the three original and fourchanged treatments was measured to study the effects of the following-up fertilization reforming on the CO2 flux in red paddy soils with different fertilities in 2012—2013. The results clearly showed that the following-up changing of fertilization had obvious impacts on the dynamics of CO2 flux. The CO2 flux in the soils under long-term organic fertilization treatments decreased after the adjustment from organic fertilization to chemical fertilization. However,the CO2 flux in the soils under long-term chemical fertilization treatments increased remarkably after the adjustment from chemical fertilization to organic fertilization. The results also indicated that both organic fertilizer and soil organic carbon( SOC) had important impacts on CO2 flux. The amount of organic carbon inputted by organic fertilizers had a significantly positive relationship with the total amount of annual CO2-C flux( r = 0.9015**,n = 21),and the inherent SOC content( x) also had a positive relationship with the total amount of annual CO2-C( y)( y = 10. 962x- 68. 86,R2= 0. 7507,n = 9,P 0. 01) in the paddy soils received chemical in 2012. The fertilization reforming from organic fertilization to chemical fertilization would lead to the loss of SOC in paddy soils due to its mineralization,and the SOC loss increased with the rising of inherent SOC content. The SOC content in the paddy soils under long-term organic fertilization would be consistent with that in the paddy soils under long-term chemical fertilization after the fertilization reforming from organic to chemical fertilization for a certain time. The fertilization reforming from chemical to organic fertilization,or from low organic to high organic fertilization would lead to the SOC accumulation in paddy soils,and the accumulating rate of SOC had a positive relationship with the amount of the inputted organic material. Under same organic fertilization treatment,the apparent decomposition rate of organic material applied in the soils with high SOC content was larger than that in the soils with low SOC content,which would result in lower SOC accumulation. So,the paddy soils with different SOC content would have the same SOC level when they received same organic fertilization management for a certain time. As a conclusion,the sustained organic fertilization in red paddy soils with high or low SOC content is essential to maintain or improve the soil organic carbon content in Southern China.