Effect of comprehensive fertilizer management on function of rice rhizosphere microbial community
Integrated fertilizer management(IFM)with a higher N dose and more fertilizer splits has been designed to increase rice yield for the full double rice system instead of for farmers in the subtropical regions of China.Higher levels of chemical fertilizers negatively affect the environment and microbial ecolo-gy,but more splits to meet plant demand might reduce adverse effects and promote soil function.A field experiment for double rice cropping conducted in 2013-2014 was used to study whether integrated fertilizer management has beneficial effects on the microbial community and microbial function compared with con-ventional practices of farmers(FP).A randomized block including integrated fertilizer management(IFM)and conventional practices of farmers(FPs)was designed.Rhizosphere and non-rhizosphere soils were col-lected at three time points during the season of growing late rice to investigate the chemical properties and enzyme activity in soil.The phospholipid fatty acids(PLFA)were used to identify microbial biomass and community composition.The results showed that IFM treatment reduced the ratio of Gram-positive bacteria(GP)to Gram-negative bacteria(GN)and the index of microbial stress in rhizosphere soil compared with the FP treatment.IFM promoted the activity of sucrase,acid phosphatase,and arylsulfatase in the rhizo-sphere soil at the stage of panicle differentiation and full-heading,while inhibiting the activity of urease at the stage of maturity.The results of analyzing redundancy showed that available nitrogen and total nitrogen explained 15.9%and 12.5%of the variability in the microbial community and enzyme activities,indicating that N availability and its level play key roles in regulating the microbial community and enzyme functions in paddy soil.The enzyme activity was significantly explained by Gram-negative bacteria(GN,5.39%),fungi(3.88%)and AM fungi(3.09%).The index of microbial stress was negatively correlated with the activity of phosphatase and sucrase,indicating that both bacteria and fungi are involved in the regulation of enzyme activity in soil.It is indicated that IFM mainly regulates the rhythm of nitrogen incorporation in pad-dy soil to change the composition of microbial communities,thereby enhancing enzyme activity in soil be-fore maturity and promoting nutrient cycling during the growth of rice.
integrated fertilizer managementmicrobial communityindex of microbial stressenzyme activitypaddy soil
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