Effect Of Long-term Fertilization On Soil Carbon Fractions And Microbial Characteristics In A Rice-wheat Rotation System

Rational application of organic fertilizer is an effective measure to improve soil quality and increase soil carbon sequestration,which also plays an important role in the sustainable utilization of farmland ecosystem.Based on the established long-term fertilizer experiment,we investigated the contents of soil carbon fractions,extracellular enzyme activities and microbial community compositions,under the application of nitrogen(N)fertilizer,N and phosphate(P)fertilizer,NP and potassium(K)fertilizer,manure,manure plus NPK fertilizers.The carbon fractions include soil organic carbon(SOC),microbial biomass carbon(MBC),dissolved organic carbon(DOC),hot water-soluble carbon(HWSC),particulate organic carbon(POC),light fraction of organic carbon(LFOC),active carbon pool and passive carbon pool.The interaction between soil carbon transformation and microbial community under long-term fertilization in a rice-wheat regime were researched in this study.The major findings were as follows:(1)The contents of soil labile organic carbon,including MBC,DOC,HWSC,POC,LFOC,were increased under the application of manure plus inorganic fertilizers.Manure application increased the carbon management index and enhanced soil fertility.The contents of dissolved organic carbon,particulate organic carbon and light fraction organic carbon could indicate the early change of soil carbon pool.(2)Application of manure plus inorganic fertilizers significantly enhanced the activities of phosphate,?-glucoside,?-cellobiosidase,N-acetyl-glucosaminidase,?-xylosidase,?-glucosidase,L-leucine-aminopeptidase and peroxidase.As the activities of ?-xylosidase,?-glucosidase and so on increased,the contents of MBC,POC and HWSC increased.(3)After wheat harvest,the relative abundance of actinobacteria,gamma-proteobacteria,Sphingobacteria and TK10 significantly increased under the treatment of manure with inorganic fertilizers,while decreased the relative abundance of Anaerolineaceae,Gemmatimonadetes and S085.After rice harvest,the application of manure plus inorganic fertilizers significantly enhanced the relative abundance of actinobacteria,Alpha-proteobacteria and Gamma-proteobacteria,but decreased the relative abundance of Bacilli,Bacteroidia,Clostridia,SBR1076,Verrucomicrobiae,Anaerolineae and S085.The increases of actinobacteria,Alpha-proteobacteria and Gamma-proteobacteria abundance,and the decreases of Anaerolineacea,S085,SBR2076 abundance,significantly enhanced the activities of oxidase and hydrolase,which further increased the contents of HWSC,LFOC and other labile organic carbon.(4)The application of manure with inorganic fertilizers significantly favor the growth of Humicola and Staphylotrichum,but inhibited the growth of Pithomyces,Pithomyces and Paraphaeosphaeria.As the relative abundance of Curvalaria,Pithomyces,Trichoderma Paraphaeosphaeria,etc.increased,and the relative abundance of Humicola increased,the enzyme activities,such as L-leucine-aminopeptidase,significantly enhanced,which further increased the contents of MBC,HWSC,POC and so on.Above all,the application of manure plus inorganic fertilizers significantly increased the relative bacterium abundance of actinobacteria,Alpha-proteobacteria and Gamma-proteobacteria and the relative fungal abundance of Humicola and Staphylotrichum,while decreased the relative abundance of Anaerolineacea,S085,SBR2076,Pithomyces,Paraphaeosphaeria,etc.,which further increased the hydrolase and oxidase activities and finally increased the contents of labile organic carbon,such as MBC,HWSC,POC,LFOC and so on.