Effects Of Long-term Fertilization On Carbon, Nitrogen Fractions And Microbial Diversity In Red Paddy Soil

Based on a 27 years long-term fertilization experiment for red paddy soil in subtropical region, by four different fertilization models:1) No fertilization(CK),2)fertilizer(NPK),3)fertilizer plus cattle manure(NPKM),4) fertilizer plus rice straw(NPKS),the paper studied the different compositions and accumulation features of soil organic carbon and nitrogen, elucidated the correlation between the component of carbon and nitrogen, revealed the response mechanism of microbial diversity to different fertilization models. The main conclusions of the paper are as follows.(1)Fertilization were favorable for promoting the transformation of water-stable micro-aggregates(<0.25 mm)into water-stable macro-aggregates(>0.25 mm), improving the mean weight diameter of aggregates. Fertilizer plus rice straw can increase the content of carbon about >0.25mm sized water-stable aggregates, Fertilizer plus cattle manure can improve the content of carbon in different sized water-stable aggregates, the long-sustain input was the factor that the content of soil organic carbon can improve.(2) Long-term fertilization can improve the content of activated carbon components, increase the ratio of activated carbon to total carbon. The fertilizer NPK plus cattle manure was favorable for increasing the content of microbial biomass carbon and light fraction carbon, the fertilizer NPK plus rice straw was favorable for increasing water-soluble carbon.(3) The content of carbon,nitrogen had no significant deficiency under no fertilization for red paddy soil, depended on the cycle of carbon and nitrogen in farmland ecosystem, which can realize the balance of soil carbon and nitrogen.(4) Long-term fertilization can improve the content of soil organic carbon and components. The fertilizer NPK plus cattle manure can increase the soil non-acid hydrolysis nitrogen and total hydrolysable N, the fertilizer NPK plus rice straw was favorable for increasing Ammonium N. (5)Fertilization can increase the richness and diversity of soil microbial communities, improve the content of soil microbial biomass,actinomycetes and Gram-negative bacteria, the effect of NPKM is better than NPK or NPKS. Long-term fertilization has a significant reflect in microbial flora, there is no difference between the NPK and NPKS, but there is a significant difference about NPKM.(6)There was a significant correlation between total carbon,total nitrogen and microbial PLFA. Following the fertilizer NPK plus the organic material, the reserve of soil carbon had increased, the content of nitrogen can accumulate; As the driving force of the cycle of carbon and nitrogen, the content of microbial PLFA had improved.