| Phosphorus is one of the essential nutrients for plant growth,however,the availability of phosphorus is generally low from soil to plants.We studied the calcareous fluvo-aquic soils and weakly acidic yellow brown soils following the long-term fertilization experiments of wheat-sweet potato rotation system.The soil samples were selected from sweet potato season to explore the effect of long-term fertilization on soil phosphorus fractions and soil biochemical properties.We aimed to study the contribution of key P fractions to yields and to investigate the roles of microorganisms in inorganic phosphorus activation and organic phosphorus transformation.The results show that as follows:（1）In yellow-brown soils,there was no significant effect on sweet potato yield and above-ground biomass under NK,NPK and NPKM treatments.Compared to CK treatment,the available P contents were 1.6,8.1 and 4.3 times in NK,NPK and NPKM treatments,respectively.Soil Ca-P contents were significantly increased by 67.0%,12.7%and 17.2%for NK,NPK and NPKM treatments,respectively.Ca-P,available P and LOP are the important P fractions for yields.The available P was significantly and positively correlated with Al-P and Fe-P.In fluvo-aquic soils,compared with CK treatment,the yields under NK,NPK and NPKM treatments were significantly increased by 44.5%,147%and 168%.The available P contents were 1.1,1.8 and 25.3 times in NK,NPK and NPKM treatments,respectively.Soil organic P and available P were more important for the yields.While Ca2-P,Ca8-P and highly resistant organic phosphorus had the higher correlation with available P.（2）In yellow brown soils,compared to CK treatment,the soil p H were decreased1.63,1.66 and 1.15 in NK,NPK and NPKM treatments,respectively.Soil microbial biomass carbon,nitrogen,phosphorus contents and soil invertase,urease,alkaline phosphatase activities were decreased under chemical fertilization（NK,NPK）.And organic fertilization had an alleviative role in decreasing of soil microbial traits.In addition,soil phytase activity were increased by 10.0%,44.3%and 75.6%.Yield and soil P contents were mainly regulated p H and phytase.The soil microbial biomass and enzyme activities were siginificantly and positively correlation with p H.In fluvo-aquic soils,fertilization significantly improved the microbial biomass and enzyme activity,which was the highest under organic fertilization treatment.The organic carbon was the main factor driving the soil enzyme activity and phosphorus fractions,and soil organic carbon regulates Fe-P,Ca2-P,LOP contents and alkaline phosphatase,phytase.（3）In yellow brown soils,P fertilization significantly affected the diversity of pho D microorganisms.At the phylum level for harboring-pho D microorganisms,actinomycetes and proteobacteria had the highest abundance,while proteobacteria had higher relative abundance for harboring-pqqc microorganisms.Soil p H was the most important factor that drives pho D and pqqc microbial community composition.In fluvo-aquic soils,the composition of harboring-pho D and-pqqc microbial communities was mainly regulated by soil carbon and nutrients（total nitrogen,available phosphorus,available potassium）.Soil organic carbon was the most critical factor driving the composition of pho D microbial communities.Total nitrogen and available phosphorus were the most critical factors for driving pqqc microrganisms community compositon.In conclusion:compared with the fluvo-aquic soils following long-term P fertilization,the yellow brown soil without P fertilization for ten years does not affect the yield due to soil phosphorus limitation.But the long-term fertization causes soil acidification and influences the soil microbial biomass and microbial function.In different soil types,the biotic and abiotic factors affect the distribution of soil inorganic and organic phosphorus fractions.Therefore,this study provides a theoretical basis for rational application of P fertilization and optimizing the fertilization measures in different soil types for planting sweet potato. |
