Effects Of Corn Straw Returning Combined With Phosphate Fertilizer On Soil Phosphorus Fractions And Yield

The abundance-deficiency and supply of phosphorus in soil directly affect the growth and development of crops.In order to improve the yield of corn,a large amount of phosphate fertilizer was applied in the agricultural production,but the utilization rate of phosphate fertilizer is only 10%to 25%.Long-term application of chemical phosphate fertilizer leads to a large accumulation of phosphorus in soil,resulting in a great waste of phosphorus resources.Songnen Plain,the main corn producing area in China,has a large area of continuous corn cropping and a large amount of straw is left over.Straw returning can not only solve the environmental pollution caused by straw burning,but also return the phosphorus in the straw to the soil.It helps reduce the adsorption and fixation of phosphorus and activate the insoluble phosphorus in soil,thus replacing part of the chemical phosphate fertilizer.The combination of straw returning with phosphate fertilizer is of great significance to coordinate and promote the efficient utilization of straw resources and the rational application of phosphate fertilizer.A frame culture and continuous positioning experiment was carried out in the middle part of Songnen Plain from 2016 to 2019,where corn was continuously planted.The two-factor split-plot design was adopted in this experiment,the main plot was straw returning method with no straw returning?S0?,straw burying?S1?and straw burning?S2?,and the sub-plot was phosphorus application level with 0?P0?,34.50?P1?,69.00?P2?and 103.50?P3?kg ha^-1?P₂O₅?.The effects of straw returning method and phosphorus application rate on soil phosphorus fractions,soil phosphatase activity,soil phosphorus adsorption-desorption characteristics,the phosphorus absorption and utilization and yield of corn were systematically studied.The results showed that:Both straw returning method and phosphorus application rate significantly affected soil available phosphorus content.Under the same phosphorus application level,compared with S0treatment,both S1 and S2 could increase soil available phosphorus content;however there was no significant difference between S1 and S2.Among them,under no phosphorus application?P0?,the effect of increasing the content of available phosphorus was the most obvious,with the increase of phosphorus application rate,the effect gradually weakened.Under the same straw returning method,with the increase of phosphorus application rate,the content of soil available phosphorus increased gradually.The effect of straw returning on soil phosphatase activity was greater than that of phosphorus application.Under the same phosphorus application level,the activities of alkaline,acid and neutral phosphatase of S1 treatment were significantly higher than those in S0 and S2 treatment,but there was no significant difference between S0 and S2 treatment.Among them,when no phosphate fertilizer was applied for three consecutive years?P0?,S1 treatment had the greatest increase in soil alkaline phosphatase activity.Under the same straw returning method,with the increase of phosphorus application rate,the soil phosphatase activity first increased and then decreased,with the maximum value at P2 level,and it was inhibited under high phosphorus?P3?level.Both straw returning method and phosphorus application rate significantly affected soil phosphorus fractions.Compared with S0 treatment,S1 treatment significantly increased the contents of soil phosphorus fractions except for Na OH-Pi,among which Na HCO₃-Po?23.80%?and Na OH-Po?9.09%?showed the largest increase,while Residual-P?3.62%?displayed the least increase.Compared with S0 treatment,S2 treatment significantly increased the contents of soil phosphorus fractions,among which H₂O-P?15.08%?and Na HCO₃-Po?13.76%?had the largest increase,while HCl-P?3.50%?and Residual-P?3.50%?had the least increase.With the increase of phosphorus application rate,the contents of soil phosphorus fractions increased gradually,among which H₂O-P?35.96%?,Na HCO₃-Po?26.07%?and Na OH-Pi?14.29%?displayed the largest increase,while HCl-P?4.29%?and Residual-P?2.87%?had the least increase.Both the application of phosphate fertilizer and straw returning?S1,S2?helped reduce the proportion of non-labile P in total P and increase the proportion of labile P in total P.The proportion of middle labile inorganic P?Na OH-Pi?in total P was increased by increasing phosphorus application,and the proportion of middle labile organic P?Na OH-Po?in total P was increased by burying straw to the field.The effect of straw returning?S1,S2?on the increase of soil phosphorus fractions was affected by phosphorus application level.Under no phosphorus application?P0?,compared with S0 treatment,the contents of soil phosphorus fractions under S1 and S2 treatment showed the largest increase,while the increasing extent was significantly reduced at high phosphorus?P3?level.Under no phosphorus application?P0?,the proportion of non-labile P in total P was significantly reduced and the proportion of labile P in total P was significantly increased under S1 and S2 treatment compared with that under S0 treatment,while the change range was significantly smaller at high phosphorus?P3?level,and the difference was not significant.Both straw returning method and phosphorus application rate significantly affected the phosphorus adsorption and desorption characteristics of black soil.Under the same phosphorus application level,compared with S0 treatment,both S1 and S2 could reduce the phosphorus adsorption capacity and increase the phosphorus desorption amount and rate of soil.Among them,the difference was the most significant under no phosphorus application?P0?,but not significantly under high phosphorus application?P3?.However,there was no significant difference between S1and S2.Under the same straw returning method,with the increase of phosphorus application rate,the phosphorus adsorption amount of soil decreased gradually,while the phosphorus desorption amount and rate increased gradually.The standard phosphorus requirement?SPR?under different phosphorus application treatments ranged from 71.02 to 91.67 kg ha^-1,of which the SPR(73.58 kg ha^-1)of S1P2 was the closest to the phosphorus application level of P2(69.00 kg ha^-1),which was the appropriate phosphorus application method of black soil area in Songnen Plain.Both straw returning method and phosphorus application rate significantly affected the phosphorus content of corn.The S1 treatment significantly increased the phosphorus content in shoot of corn at the three-leaf and jointing stage.Both S1 and S2 treatment significantly increased the phosphorus content in shoot and cob of corn at the maturity stage,but there was no significant difference between S1 and S2 treatment.With the increase of phosphorus application rate,the phosphorus content of corn increased gradually.When the phosphorus application reached P2 level at the jointing and maturity stage,the phosphorus content of corn shoots was not significantly increased by continuous application of phosphate fertilizer?P3?.The effects of straw returning method and phosphorus application rate on corn yield did not show a consistent pattern in two years.Under the same phosphorus application level in 2018 and2019,there was no significant difference in corn yield among different straw returning methods.In2018,with the increase of phosphorus application rate,corn yield increased gradually,but there was no significant difference among different phosphorus application levels;in 2019,with the increase of phosphorus application rate,corn yield increased gradually,and there was a significant difference between phosphorus application and no phosphorus application.