Effects Of Straw And Nitrogen Fertilizer On Phosphorus Transformation And Leaching Loss In Yellow Brown Soil

Phosphorus is an essential nutrient element for crop growth.The annual input of phosphorus fertilizer in China is increasing,but the utilization rate of phosphorus fertilizer in that season is very low,and a large amount of phosphorus is accumulated in the soil.Soil phosphorus accumulation is not only a waste of phosphorus resources,but also brings a certain risk of phosphorus loss.As an important agronomic measure,the mixed application of straw and nitrogen can reduce the fixation of soil accumulated phosphorus by improving soil microbial activity.However,the effect of the mixed application of straw and nitrogen on the activation of accumulated phosphorus and whether it will increase the risk of phosphorus loss are still unclear.Therefore,in this study,soil F with long-term phosphorus fertilizer and soil O with long-term organic fertilizer were selected as the research objects.Four treatments,control(CK),adding straw(S),adding nitrogen fertilizer(N)and mixed application of straw and nitrogen fertilizer(SN),were set up respectively.The culture experiment was carried out at25 ℃.At the same time,the rainfall leaching simulation experiment was carried out by using soil column.By analyzing the changes of soil phosphorus component content and phosphorus loss amount and form in leaching solution,to explore the effects of straw and nitrogen fertilizer on the transformation of soil accumulated phosphorus components,phosphorus loss forms and phosphorus loss laws.The main results are as follows:(1)The inorganic phosphorus content of soil f decreased by 4.12% and 4.79% respectively,and the inorganic phosphorus content of soil o decreased by 2.49% and 9.86% respectively;Straw treatment,nitrogen treatment and mixed application of straw and nitrogen increased the organic phosphorus content of the two soils.The organic phosphorus content of soil f increased by 3.87%,4.93% and 6.89% respectively,and the organic phosphorus content of soil o increased by 1.79%,3.60% and 2.42% respectively.(2)In soil F,the combined application of straw and nitrogen will promote the activation of accumulated phosphorus.In soil F,the mixed application of straw and nitrogen increased the content of high active phosphorus by 2.04%,decreased the content of stable phosphorus by0.97%,and decreased the content of medium active phosphorus by 1.07%;In soil O,the mixed application of straw and nitrogen increased the high active phosphorus component by 3.30%,decreased the medium active phosphorus component by 3.06%,and increased the stable phosphorus component by 6.36%.(3)In the four treatments,the main form of inorganic phosphorus is orthophosphate,and the main form of organic phosphorus is orthophosphate monolipid.In soil F,straw treatment,nitrogen treatment and mixed application of straw and nitrogen will increase the content of orthophosphate and orthophosphate monolipid.The content of orthophosphate increased by18.56%,20.8% and 21.11% respectively,and the content of orthophosphate monolipid increased by 10.4%,28.49% and 18.91% respectively;In soil O,straw treatment,nitrogen treatment and mixed application of straw and nitrogen will reduce the content of orthophosphate by 72.56%,12.27% and 30.94% respectively.(4)Straw combined with nitrogen fertilizer treatment will significantly increase the content of microbial carbon and soluble organic carbon,increase the total amount of bacteria and fungi,increase the content of Microbial Phosphorus,promote the transformation of soil stable phosphorus components into highly active phosphorus components,transform soil inherent phosphorus components into soil solution phosphorus components,and improve the supply capacity of soil phosphorus.However,under rainfall factors,the loss of soil soluble phosphorus and total phosphorus is increasing,activated phosphorus in soil further increases the risk of phosphorus loss.(5)The mixed application of straw and nitrogen will increase the loss of soluble phosphorus,granular phosphorus and total phosphorus in the leaching solution by 0.09 mg P/kg,0.11 mg P /kg and 0.20 mg P /kg respectively.The loss of soluble phosphorus accounts for71.87% of the total phosphorus loss,which is the main form of total phosphorus loss,and the loss of soluble inorganic phosphorus accounts for 92.87% of the soluble phosphorus loss,which is the main form of soluble phosphorus loss.Straw addition will increase the risk of phosphorus loss,and the loss of total phosphorus in straw addition treatment increased by 0.15 mg P /kg.Nitrogen addition had no significant effect on phosphorus loss.By quantifying the change trend of different forms of phosphorus components and the loss of different forms of phosphorus in soil after straw returning and nitrogen fertilizer,this study observed the activation of soil accumulated phosphorus and the risk of phosphorus loss after activation,so as to provide a basis for improving the effectiveness of soil accumulated phosphorus and preventing agricultural non-point source pollution.