Effects of Long-Term Fertilization on Dynamics of Soil Organic Carbon in Red Paddy Soil

A long-term field experiment has been going on for 23 years in Jinxian County,Jiangxi Province,One of its aims was to study effects of long-term fertilization on dynamics of soil organic carbon(SOC)in red paddy soil.For that purpose,four treatments were designed and laid out:(1)No fertilization(CK),(2)chemical fertilizer alone(NPK),(3)organic manure alone(OM)and(4)combination of chemical and organic fertilizers(NPKM).Results showed that the content of SOC was still increasing after 23 years of experiment,especially in Treatments OM and NPKM,where the increase was in positive linear relationship with the year.The content of SOC in the profile decreased in the sequence of APW_1 W_2 in all treatments,showing a decreasing trend with the depth in profile.Long-term fertilization affects mostly the content of SOC in the topsoil.The storage of SOC was increasing with the year,but decreased in the sequence of NPKMOMNPKCK in all profile horizons. Application of organic manure could promote sequestration of soil organic carbon.The findings of the experiment were expected to improve understanding of the effects of fertilization on dynamics of SOC and SOC pool,and on distribution and storage of SOC,and provided some theoretical facts for understanding effects of agricultural soil on global cycling of carbon.