Effects Of Rice Straw Application On The Rapeseed Rhizosphere Microbial Communities In Rice-rapeseed Rotation Systems

Returning straw to soil is an economic and sustainable way in agriculture for the improvement of soil conditions,thus to increase crop production.The microbial responses to this―green‖fertilization in different type of soils have been investigated in recent years.However,how specific rhizosphere microbial communities were affected by the rice straw application in the long-term rotation system remains unclear.Two different types of soils which have been cultivated under rice-rapeseed rotation for several years were used to explore the shift of the rapeseed rhizosphere functional microbial community due to the rice straw amendment.Two treatments consisted of the rice-straw amendment and the control for seven years.Soil samples were collected in 2013-2014 at four indicated points corresponding to distinct stages of rapeseed development:wintering,bolting,flowering and ripening(20 soil samples).Initially,soil physicochemical properties and enzymatic activities were characterized.Soil microorganisms were investigated using community-level physiological profiles(CLPP),phospholipid fatty acid analysis(PLFA)and high-throughput sequencing analysis.The results are as follows:There were no notably differences in TN,C/N,TP and TK between the straw application(SA)and control(NSA).In contrast,AN,AP,and AK were found to significantly increase,indicating that the rice straw amendment affected available nutrients.Soil enzyme activities(phosphatase,invertase,aryl sulfates and urease)in soils were significantly restricted by AK in Jingzhou,but they were controlled by TC and AN in Wuxue.The Jingzhou NSA soil at wintering stage clustered with SA soil,while the Wuxue NSA and SA soil were clearly distinguished,indicating that the Wuxue soil microbial communities responded to the rice straw application rapidly compared to Jinghzou.The microbial functions,indicated by Eco-plate data,at both sites were enhanced within SA fields.The utilization rates of the main carbon source by microbes were different between the two soil types.Rice straw application increased the carbon source utilization of amino acids and phenolic acid.PLFA data indicated that the rice rice application increased the soil microbial biomass.The soil microbial biomass in Jingzhou was significantly increased at flowering and ripening stages,while that in Wuxue was increased at bolting,flowering and ripening stages.The effect of rice straw application on the rhizosphere microbial community was clear distinguished earlier in Wuxue,which was similar with the result of the enzyme activities,indicating that Wuxue soil microbial communities responded to the rice straw application rapidly compared to Jinghzou.Redundancy analysis showed the rapeseed rhizosphere microbial communities at Jingzhou were significantly influenced by the soil physicochemical properties including K and MOI(P<0.05)while those at Wuxue were significantly(P<0.05)shaped by P.The microbial community was primarily grouped by geographic sites,and the microbial communities at the two fields were distinguished by the relative abundances of actinomycetes,Fungi,GN~-bacteria,AM Fungi,and anaerobes.The profiles of high-throughput sequencing revealed that there were significant differences the bacterial community structure across the stage,suggesting that the plant can select a subset of microbes at different stages of growth.The bacterial community was primarily grouped by geographic sites through the clustering analysis of the bacterial community in the phylum,indicating that the bacterial community was significantly influenced by soil types.Additionally,Acidobacteria,Chloroflexi,Bacteroidetes and Actinobacteria significantly changed with rapeseed development in Jingzhou SA soils,while Acidobacteria,Actinobacteria,Nitrospirae and Verrucomicrobia significantly changed in Wuxue.The data obtained in this study would provide valuable information for a better under standing of the effect of rice straw application on the rapeseed rhizosphere microbial communities in two rapeseed-rice rotation systems.CCA of the OTUs and soil physicochemical properties showed the rapeseed rhizosphere microbial communities at Jingzhou were significantly influenced by the soil physicochemical properties including K and MOI(P<0.05)while those at Wuxue were significantlyshaped by P and MOI(P<0.05).The data presented in this study suggested that the rice straw application at different sites had a diverse influenced on microbial community structure and function of the rapeseed rhizosphere,which provided the theoretical basis for the promotion of straw returning to field as an alternative fertilizer application to increase grain yield...