| 【Objective】The growth and metabolism of plant and microbe are almost enzymatic reactions,soil enzyme activity can directly express its biological activity.Therefore,the objective of this experiment was to study the effects of exogenous nutrient input on soil microbial activity and phosphatase activity which was closely related to the phosphorus cycle in paddy soil,so as to clarify the responses of the phosphorus activity to carbon and phosphorus additions in rice rhizosphere and bulk soils.It is of great significance to guide the fertilization and management of rice soil and to realize the sustainable utilization of farmland.【Method】The typical phosphorus-limited rice soil in Hunan was selected for pot experiment.The treatments include:no carbon and phosphorus addition（CK）,carbon addition（C）,phosphorus addition（P）,carbon and phosphorus addition（CP）.Acid phosphatases（ACP）and alkaline phosphatases（ALP）of the rhizosphere and bulk soils were determined by 96-microtiter plateau method.4 soil phosphorus based on the biological availability（CaCl2-P,Citrate-P,Enzyme-P and HCl-P）were measured by biologically based phosphor（BBP）method.To investigate the response of carbon and phosphorus addition and 4 soil phosphorus components based on the biological availability to soil enzyme activity.At the same time,the spatial and temporal distribution of rhizosphere enzyme activity was studied by in situ zymography to explore the relationship between rhizosphere enzyme activity and hotspot area.The treatments include:no carbon and phosphorus addition（CK）,carbon addition（C）,phosphorus addition（P）,carbon and phosphorus addition（CP）.【Result】Compared with CK,the above-ground biomass of C,P and CP significantly increased by 29.76%,84.03%and87.94%,respectively（P<0.05）,the underground biomass significantly decreased by20.13%and increased by 57.49%and 56.53%,respectively（P<0.05）,which was consistent with the content of plant P（P<0.05）.The results showed that pH,the contents of NH4+-N and Olsen-P in rhizosphere soil were significantly lower than those in bulk soil（P<0.05）.The content of MBP in rhizosphere soil（except CP treatment）was significantly lower than that in bulk soil（P<0.05）.Carbon and phosphorus additions had a significant regulatory effect on 4 soil phosphorus components based on the biological availability in paddy rhizosphere and bulk soils（P<0.05）.Olsen-P and MBP had a significantly negative correlation with ALP（P<0.05）,but no significantly correlation with ACP,indicating it is obvious for microbes to utilize available nutrients.Phosphatase activity in bulk soil was mainly affected by pH,NH4+-N and MBP,as well as CaCl2-P and Citrate-P content,while soil water content,Olsen-P,DOC and root biomass,as well as HCl-P and Enzyme-P contents mainly affected phosphatase activity in rhizosphere soil.Soil C/P ratio significantly affected the activities of ALP and ACP.In situ zymography technology,unlike the method that the soil homogenization to measure enzyme activity,from two-dimensional visualization of the spatial and temporal distribution of enzyme activity studied,and found that the hotspot is located in the relatively high enzyme activity area in the rhizosphere,acid phosphatase spread along rhizosphere distribution,alkaline phosphatase relatively dispersed throughout the region,the area of the hotspot will be expanded over time.【Conclusion】The application of P and CP addition could improve the microbial activity of phosphorus-limited rice soil,increase the biomass significantly,and improve the rhizosphere microbes benefit and amendment the soil environment as well as benefit the health of paddy field ecosystem. |
