Effects Of Straw Returning Combined With Slow And Controlled Release Fertilizer On Nutrient Uptake And Soil Nitrogen In Wheat-Maize Rotation System

As an important agricultural production base in Anhui Province and even the whole country,winter wheat-summer corn is the main planting pattern in Huang-Huai-Hai Plain.However,at present,the Huang-Huai-Hai region is faced with the problems of unreasonable fertilization structure,low nutrient resource utilization efficiency and low straw utilization rate.Therefore,reducing nitrogen loss and nitrogen accumulation in soil under the premise of ensuring food security is of great significance to reducing agricultural non-point source pollution in the Huang-Huai-Hai plain.In this study,field experiments were conducted to explore the dynamic distribution characteristics of crop yield,nitrogen uptake,nitrogen nutrient efficiency and soil available nitrogen content under the condition of straw returning,and to provide basis for the optimization of fertilization mode and the integration of non-point source pollution prevention and control technology in wheat-jade-crop rotation area.And according to the results of field experiment,the design of indoor simulated soil culture experiment explores the urea slow-release urea and adding nitrification inhibitor 3,4-dimethyl pyrazole phosphate(DMPP)on soil nitrogen form and its transformation,the influence of available nitrogen and slow release nitrogen fertilizer one-off fertilization technology mode of nitrogen loss prevention and control to provide technical support and new product research and development basis.The main research is as follows:(1)The field experiment consisted of no fertilization(CK),straw returning(S),recommended fertilization(F),straw returning + recommended fertilization(SF),and straw returning + controlled release fertilizer + slow-release fertilizer(SCU).The results showed that SCU had no significant effect on wheat yield compared with no fertilization treatment,but increased yield by 5.8% in maize season compared with conventional fertilization treatment.The annual yield increase rate was the same as that of conventional fertilization,and there was no significant difference in aboveground nitrogen uptake(P<0.05).Both straw returning and fertilization treatments could effectively improve soil fertility in the surface layer.The content of ammonium nitrogen in the surface layer of SCU treatment reached the peak value at heading stage(21.28mg/kg),which was significantly higher than that of SF(7.00 mg/kg)(P<0.05)to provide sufficient nutrients for the critical growth period of wheat.At the maturity stage of maize,the content of nitrate nitrogen in the lower soil layer of SCU was higher than that in the upper soil layer,and the high concentration of nitrate nitrogen was maintained for a long time,which increased the risk of vertical migration of nitrogen.(2)Seven treatments,including no fertilization(CK),urea application alone(N),sustained release urea application alone(S),60% urea +40% sustained release urea(NS),urea +DMPP(ND),sustained release urea +DMPP(SD),60% urea +40% sustained release urea +DMPP(NSD),were set in the laboratory experiment.The content of ammonium nitrogen in ND treatment was significantly higher than that in N treatment(P<0.05)and effectively delayed the conversion time of ammonium nitrogen to nitrate nitrogen.Compared with S treatment,SD treatment significantly increased the content of ammonium nitrogen in soil(P<0.05),and the effective action time of nitrification inhibition was about 49 d.During this period,the apparent nitrification rate was decreased and the nitrification inhibition rate was increased.Compared with NS treatment,NSD treatment not only significantly increased soil ammonium nitrogen content(P<0.05),the half-life of ammonium nitrogen was prolonged to 18.6 d,and the nitrification inhibition rate was significantly increased(P<0.05),and the effective inhibition time of apparent nitrification was extended about 32 days.The comprehensive analysis showed that the combined application of urea and sustained-release urea with DMPP had an obvious effect on the inhibition of ammonia oxidation,and significantly increased the nitrification inhibition rate(P<0.05),reduced the apparent nitrification rate,and effectively prolonged the residence time of ammonium nitrogen in the soil.