Response Of Soil Microorganisms To Phosphorus Change With Tillage Years For Maize And Rice Growth In Black Soil

Phosphorus is an indispensable nutrient and non renewable resource for plant growth.In agricultural production,the utilization rate of the crops is only 10%?25%after the exogenous phosphate fertilizer is applied to the soil.The effectiveness of soil phosphorus is affected by soil properties,soil types,tillage methods,fertilization methods.Black soil,as a kind of soil with internal productivity and high fertility,has been reducing soil nutrients in recent years,which affects grain production.At present,the researches on black soil mostly focus on the changes of physical and chemical properties,and there are relatively few researches on soil phosphorus and its microbial community and the response process of functional genes.Soil microorganism is the key driving factor in the process of phosphorus biogeochemistry.Therefore,this study selected soils of different planting types(upland and paddy)in the black soil area as the research object to study the evolution of soil phosphorus pool and its microbial response process with the increase of tillage years.Researches show that:1.The results showed that the Available-P and Residual-P contents increased significantly with the increase of tillage years(p<0.05),but Po,Secondary-P and Primary-P did not change significantly.Among them,the contents of Available-P and Residual-P increased from 12.56 mg/kg and 89.83 mg/kg in the 10th year to 21.59mg/kg and 201.1 mg/kg in the 60th year,respectively,indicating that long-term fertilization resulted in the phosphorus not absorbed and utilized by plants being gradually fixed by soil minerals to become stable phosphorus.By comparing stoichiometry,with the increase of fertilization years,soil TC/TP decreased significantly(p<0.05),but the ratio of MBC/MBP did not change significantly.Further analysis of microbial community composition,soil phosphatase activity and related functional genes(phoD)showed that with the increase of planting years,microbial community composition(phospholipid fatty acid PLFAs determination)did not change significantly,long-term tillage of maize only resulted in a significant decrease in the abundance of arbuscular mycorrhizal fungi(p<0.05),but increased soil phosphatase activity(p<0.05).The absolute abundance of phoD reached the peak at 20 yr,but there was no significant change at 10 yr compared with 60 yr.However,Proteobacteria increased significantly(p<0.05),while Actinobacteria decreased significantly(p<0.05),and the dominant bacteria changed from Bradyrhizobium(10yr,20 yr)to Pseudomonas(60 yr).The results showed that gram negative bacteria(G~-,positive correlation),AMF(negative correlation)and Amycolatopsis(negative correlation)were significantly correlated with Primary-P and Residual-P.2.According to the paddy soil of different tillage years,the contents of Available-P,Po,Secondary-P,Primary-P and Residual-P increased significantly with the increase of tillage years(p<0.05).Residual-P was the most increased component of phosphorus pool,with an increase of 48.53 mg/kg.By comparing the stoichiometry,it was found that:with the increase of fertilization years,soil TC/TP did not change,but MBC/MBP decreased significantly(p<0.05),from 190.8 in the first year to 56.23in the 35th year,indicating that microbial regulation of soil phosphorus pool changed from inorganic phosphorus fixation to organic phosphorus mineralization.Further analysis of microbial community composition,soil phosphatase activity and related functional genes(phoD)showed that with the increase of tillage years,microbial community abundance increased significantly(p<0.05),and soil phosphatase activity decreased.The absolute abundance of soil phoD gene increased significantly(from2.59×10~7/g of 1 yr to 10.05×10~7/g of 35 yr,p<0.05),but the abundance and diversity decreased.With the increase of tillage years,Proteobacteria increased significantly and Actinomycetes decreased significantly(p<0.05),and the dominant bacteria changed from Rubrobacter to Cupriavidus.Further correlation analysis showed that gram positive bacteria(G~+)and AMF were correlated with Primary-P and Residual-P;Cuprophores and Streptomyces were correlated with all components of soil phosphorus pool at different levels;Rubrobacter and Pleomorphomonas were correlated with all components of soil phosphorus pool There was significant negative correlation at different levels.3.Comparing two different tillage types of soil,it was found that the availability of phosphorus in soil was significantly increased and the Residual-P content was significantly increased due to long-term fertilization.With the increase of tillage years,different from upland tillage,paddy field due to flooded anaerobic environment accelerated the release of soil phosphorus,the contents of Po,Secondary-P and Primary-P in soil increased significantly,the abundance of soil microbial community and the absolute abundance of phoD gene increased significantly,the MBC/MBP ratio decreased significantly,and the response of microorganisms to soil phosphorus pool changed from inorganic phosphorus fixation to organic phosphorus fixation mineralization is dominant.