title: Soil microbial C:N ratio is a robust indicator of soil productivity for paddy fields.
abstract: Maintaining good soil productivity in rice paddies is important for global food security. Numerous methods have been developed to evaluate paddy soil productivity (PSP), most based on soil physiochemical properties and relatively few on biological indices. Here, we used a long-term dataset from experiments on paddy fields at eight county sites and a short-term dataset from a single field experiment in southern China, and aimed at quantifying relationships between PSP and the ratios of carbon (C) to nutrients (N and P) in soil microbial biomass (SMB). In the long-term dataset, SMB variables generally showed stronger correlations with the relative PSP (rPSP) compared to soil chemical properties. Both correlation and variation partitioning analyses suggested that SMB N, P and C:N ratio were good predictors of rPSP. In the short-term dataset, we found a significant, negative correlation of annual rice yield with SMB C:N (r = -0.99), confirming SMB C:N as a robust indicator for PSP. In treatments of the short-term experiment, soil amendment with biochar lowered SMB C:N and improved PSP, while incorporation of rice straw increased SMB C:N and reduced PSP. We conclude that SMB C:N ratio does not only indicate PSP but also helps to identify management practices that improve PSP.
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.|Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.
authors.forename: Jinshui
authors.initials: J
authors.lastname: Wu
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.
authors.forename: Jianlin
authors.initials: J
authors.lastname: Shen
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.
authors.forename: Shoulong
authors.initials: S
authors.lastname: Liu
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Wang
authors.affiliation: Changsha Research Station for Agricultural &Environmental Monitoring and Key Laboratory of Agro-ecological Processes in Subtropical Regions, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Chen
authors.affiliation: Hunan Soil and Fertiliser Station, Hunan 410005, China.
authors.forename: Tieping
authors.initials: T
authors.lastname: Huang
authors.affiliation: Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, China.
authors.forename: Jiabao
authors.initials: J
authors.lastname: Zhang