Effects Of Returning Maize Straw With Controlled-release Urea Blended With Other Fertilizer On Soil Enzyme Activities And Nutrients During The Wheat Season

Straw returning is an important measure to make full use of agricultural resources and sustainable development of agriculture.With the promotion of straw returning technology,how to optimize the type,amount,time and method of nitrogen fertilizer application on the basis of straw returning has been a hot topic in agricultural research.Studies have shown that the rational combination of straw returning and nitrogen fertilizer could significantly improve soil fertility and crop yield,but about the maize straw returned and controlled-release urea blended with urea and other fertilizer long-term with impact on soil enzyme activity and soil nutrient is unclear.This study is based on two long-term positioning fertilization experiments in wheat-maize rotation.In the brown soil area,the effects of controlled-release urea blended with urea and other fertilizer（CRF）and bulk blending urea and other fertilizer（BBF）on soil enzyme activities and soil nutrients in wheat season were compared with and without maize straw returning.The interaction between whether maize straw was returned and the two types of blended nitrogen fertilizers on soil enzyme activities and soil nutrients was also analyzed.On Chao soil,straw returned is studied under the condition of two types of blended nitrogen fertilizers of CRF and BBF with no nitrogen(N 0kg·hm^-2),reduction(N 120kg·hm^-2),constant(N 240kg·hm^-2)and excessive(N 360kg·hm^-2)four nitrogen levels on the influence of the characteristic of the soil enzyme activity and soil nutrient.The main results are as follows:（1）In brown soil,CRF treatment significantly increased the activities of neutral phosphatase（rejuvenation stage and maturity stage）,sucrase（rejuvenation stage and booting stage）and cellulase（rejuvenation stage and booting stage）and the contents of soil organic matter,nitrate nitrogen and Olsen phosphorus at maturity stage compared with BBF treatment without maize straw returning to field.Among them,neutral phosphatase activity increased by29.6%and nitrate nitrogen content increased by 34.8%.（2）With maize straw returning,the activities of urease and cellulase at maturity stage and neutral phosphatase at booting stage under BBF treatment were significantly higher than those in CRF treatment in brown soil,but there was no significant difference in enzyme activities at other stages between the two types of blended nitrogen fertilizers.The contents of total nitrogen,organic matter,nitrate nitrogen and Olsen phosphorus in brown soil treated with maize straw returning combined with CRF were significantly higher than those treated with BBF at maturity.（3）Compared with non-returning maize straw,neutral phosphatase activity and sucrase activity in brown soil were increased by 10.3%～35.2%and 11.1%～37.4%,available potassium content in rejuvenation and booting stages was increased by 9.5%～63.2%,and Olsen phosphorus content in maturity stage was increased by 30.4%～50.2%.（4）On Chao soil and under straw returning,the same nitrogen level of CRF treatment than the BBF treatment sucrase activity increased by 9.6%～21.0%,cellulose enzyme activity increased by 9.0%～31.5%.The soil NO₃^--N content under CRF treatment was significantly higher than that under BBF treatment,and increased by 23.2%～145.0%at rejuvenation and maturity stages.Compared with BBF treatment,CRF treatment could increase the constant N application level at rejuvenation stage,excessive N application level at flag stage and NH₄⁺-N content of each N application level at maturity stage.（5）Under maize straw returning,the urease activity of BBF treatment with excessive N application was significantly higher than that with constant and reduced N application in Chao soil,and increased by 7.0%～30.1%.The activity of alkaline phosphatase in Chao soil was significantly affected by the amount of fertilizer application.Compared with excessive fertilizer application,the activity of alkaline phosphatase in Chao soil remained high in the whole growth stage under the condition of reduced and constant fertilizer application.In the filling stage,the alkaline phosphatase activity of constant N application increased by 6.6%～7.8%compared with that of excessive N application.In conclusion,CRF is more beneficial to increase the activities of neutral phosphatase,cellulase and sucrase in brown soil at the middle growth stage of wheat than BBF without maize straw returning.There was no significant difference in enzyme activity among different blended nitrogen fertilizer types in brown soil with maize straw returning.The activities of sucrase and cellulase in Chao soil were increased by CRF under maize straw returning.Compared with BBF treatment,CRF could significantly increase soil organic matter content and increase the supply intensity of available nitrogen and phosphorus nutrients in the later stage of wheat in brown soil and Chao soil.Constant CRF fertilization was the optimal treatment for the amount of fertilizer application,which was an efficient fertilization mode to promote the increase of wheat yield and income and the sustainable utilization of farmland.The experimental data can provide data support for the realization of sustainable agricultural development and high-yield crop nutrient management in the field and the mode of light simplified fertilization.