Effects Of Phosphorus And Straw Addition On Phosphorus Transformation In Soils With Different Phosphorus Contents

Phosphorus is an essential element in the growth and development of plants and animals.In the soil environment,up to 95%of phosphorus are in the relatively difficult-to-utilize forms.The effectiveness of phosphorus for organisms depends on its form,content,and mutual transformation.The transformation process of soil phosphorus includes the chemical transformation of insoluble inorganic phosphate and the mineralization of organic phosphorus.Phosphatases that drive organophosphate mineralization were controlled by the composition and diversity of related microbial flora,while the composition and structure of microorganisms were fed back and regulated by the content and proportion of soil nutrients.Although the effect of fertilization on soil phosphorus transformation and microbial structure composition has been studied a lot,the effectiveness of fertilizer addition on soil phosphorus with different nutrient content and the microbiological and enzymatic mechanisms based on ecological stoichiometry need to be further studied.To this end,in this study,three kinds of yellow-brown upland soil with long-term no fertilization（B）,chemical fertilizer（C）and organic fertilizer（O）were selected as the research objects.On which,six treatments were set up,including the control check（CK）,straw（S,wheat）,medium level phosphorus addition(P,30mg·P·kg^-1,KH₂PO₄),straw+P（SP）,high level phosphorus addition(PP,150mg·P·kg^-1,KH₂PO₄)and straw+PP（SPP）.A 50-day indoor incubation experiment was conducted at 25℃to observe the changes of soil available phosphorus,phosphorus forms,transformation of soil carbon and nitrogen,soil enzymes and community composition and diversity of phosphorus transformation related microorganisms.The driving mechanism of phosphorus and straw addition on phosphorus transformation and related microorganisms in long-term different fertilization soils were explored.The main findings were as follows:（1）There were significant differences in total phosphorus content and available phosphorus in soils with different long-term fertilization.The total phosphorus content in soils B,C and O were 67.5,163.1 and 912.7 mg·kg^-1,respectively,and the content of available phosphorus was 17.7,58.9 and 398.2 mg·kg^-1,respectively.Long-term application of chemical fertilizers and organic fertilizers increased the total phosphorus content of the soil by 2.4 times and 13.5 times,respectively,compared with non-fertilization;and the long-term application of organic fertilizers increased the total phosphorus content of the soil by 5.6 times compared with the application of chemical fertilizers.The activities of soilβ-1,4-glucosidase,β-1,4-N-acetylglucosaminidase,acid phosphatase and alkaline phosphatase were in the order of O>C>B,and the difference was significant（P<0.01）.（2）Phosphorus addition significantly increased the content of soil available phosphorus,soil activity,and active phosphorus components.During the cultivation period,the available phosphorus in all soils increased with the increase of phosphorus addition level.Phosphorus addition significantly increased the content of Resin-Pi/Po,Na HCO₃-Pi,Na OH-Pi,c HCl-Po,Residual-P（p<0.05）,while reduced the organic phosphorus content in soil B and C,and increased the organic phosphorus content in soil O.The contents of Resin-Pi,Na HCO₃-Pi and Na OH-Pi in the PP were significantly higher than those in the P treatment.（3）Compared with the treatment of adding phosphorus alone,the combined application of phosphorus with straw increased the content of available phosphorus in soil B and C,but the opposite was true in soil O.In the treatment of phosphorus combined with straw,Na HCO₃-Po increased significantly（p<0.05）,and d HCl-Po decreased significantly（p<0.05）.The addition of straw significantly increased the soil soluble organic carbon content and the emission flux of soil carbon dioxide and nitrous oxide.（4）Acid phosphatase dominates the three types of soils.Straw is a significant factor affecting soil phosphatase activity（P<0.01）.The phosphatase activity of treatment with straw is significantly higher than that without straw.Phosphatase did not respond significantly to phosphorus addition,but soilβ-1,4-glucosidase andβ-1,4-N-acetylglucosaminidase activities were significantly increased（p<0.05）.In the treatment of phosphorus combined with straw,the increase of acid phosphatase and alkaline phosphatase activity was consistent with the increase ofβ-1,4-glucosidase andβ-1,4-N-acetylglucosaminidase activity.It shows that phosphorus mineralization is internally coupled with carbon and nitrogen mineralization to a certain extent,and the phosphatase activity is driven by the demand of microbes for carbon and nitrogen.（5）The addition of straw and the combined application of straw and phosphate fertilizer significantly increased the absolute abundance and species diversity of phoC and phoD genes.The dominant species of phoC and phoD gene bacterial communities are mainly distributed in the Proteobacteria and Actinobacteria.Adding straw and exogenous phosphorus increase the relative abundance of Cutrophils and Brachyrhizobium.The species composition tends to develop microbial groups related to carbon and nitrogen metabolism.Long-term different fertilization changes the composition and function of soil microorganisms,and long-term application of organic fertilizer is conducive to the formation of a stable and multi-functional microbial flora.In summary,phosphorus and straw application can affect the abundance,diversity,and composition of phoD and phoC gene microbial community by changing nutrient availability,and then regulate the activities of acid phosphatase and alkaline phosphatase,affect the transformation of soil phosphorus,and ultimately affect the level of soil available phosphorus.