Responses Of Soil Microorganism And Phosphorus Migration In Paddy Field To Phosphorus Fertilizer Regulation And Straw Returning

Rice is the main food crop in China,with a long history of planting and a wide planting area.Phosphorus is one of the essential nutrients for crop growth and development.Phosphorus input is particularly important for rice growth.Straw returning or straw combined with chemical fertilizer can effectively improve soil nutrient balance,improve nutrient availability,reduce fertilizer loss rate,improve soil fertility capacity and improve soil structure.Therefore,it is particularly important to reduce fertilizer input and improve nutrient use efficiency without reducing rice yield.In this paper,by setting up a long-term locating experiment,selecting different amounts of straw returning to the field and phosphate fertilizer combined application rate,the profile distribution of soil total phosphorus and available phosphorus,rice yield,phosphorus utilization efficiency and microbial community structure change characteristics were analyzed,and the initial and long-term experiments were compared.After(5 years),soil phosphorus changes and phosphorus surplus and deficiency,etc.,to clarify the evolution characteristics of soil phosphorus fertility,microbial differences and changes in rice yield under the long-term return of straw to the field and combined application of phosphorus fertilizers in the experimental area.The main findings are as follows:1.After long-term straw returning to the field and phosphate fertilizer combined application,the total phosphorus and available phosphorus content in the soil will change.Regardless of whether the straw is returned to the field or not,the total phosphorus and available phosphorus content of 0-20cm soil layer will be significantly reduced when no phosphate fertilizer is applied for a long time,which is expressed as phosphorus deficit.After applying phosphorus fertilizer,the content of total phosphorus and available phosphorus in the 0-10cm soil layer increased,and the surplus of soil phosphorus increased.The surplus of P1-P3 phosphorus was3.46,16.23,and 29.85 kg/hm~2.After the straw is returned to the field,the surplus of soil phosphorus first decreases and then increases,and the content of available phosphorus increases,which can prevent the excessive accumulation of phosphorus in the soil while maintaining the content of soil available phosphorus.2.The soil phosphorus activation coefficient of the plough layer without phosphate fertilizer for a long time decreased,and the soil phosphorus activation coefficient increased after applying phosphate fertilizer.The phosphorus activation coefficient of P2 treatment was the highest,compared with P0 treatment,it increased by 0.35%～3.96%,respectively.After long-term return of straw to the field,the soil phosphorus activation coefficient of the plough layer increased,and the specific performance was that the S2 level was the highest,followed by the S1 and S3 levels,and the S0 level was the lowest.This indicates that the change of soil available phosphorus is synergistic with the change of the phosphorus activation coefficient.3.The dominant phyla of soil bacteria under the treatment of straw return and phosphate fertilizer did not change,but the composition ratio of the phylum classification changed.Bacterial diversity index and richness index respond differently to different amounts of straw returned to the field.The diversity index is the highest under S1 and S2 treatments,and the richness index is the highest under S1 treatment.Phosphate fertilizer has no significant effect on the bacterial diversity index.The Beta diversity classification based on species classification and phylogeny showed that the composition of S1 and S2 treatments was similar,and that of P0 and P1 treatments was similar.Both straw and phosphate fertilizer can increase the diversity index of fungi and actinomycetes.The Beta diversity classification shows that the fungal species composition of S1 and S2 treatments is similar,and that of P0 and P1 treatments is similar.4.The five-year rice yield data show that reasonable application of phosphate fertilizer(P2)and straw returning to the field(S2)can increase rice output.With further increase in the amount of phosphate fertilizer,the rice output is flat or declining,In addition,the effect of increasing the yield of straw in the late stage was greater than that in the early stage.The interaction of straw and phosphate fertilizer has a significant impact on the phosphorus utilization efficiency of rice.Too high phosphorus fertilizer application rate reduces the phosphorus utilization efficiency of rice.The partial productivity of phosphate fertilizer also decreases with the increase of phosphate fertilizer input in the soil.Returning straw to the field can improve the effect of increased application of phosphate fertilizer on the decline of partial productivity.Compared with S0,the partial productivity of S1 and S2 decreased by 53.75 and38.05 kg/kg.