Effects Of Blended Application Of Controlled-release Urea And Normal Urea With Straw Returning On Soil Microorganism And Wheat Growth

Long-term urea applications lead to soil degradation and nitrogen loss,while the slowrelease properties of controlled-release urea could reduce these effects.Controlled-release urea and normal urea with straw returning were an effective way to improve the soil nutrient and increase yields.Soil nitrogen supply and grain dry matter accumulation during this period had an important influence on the final yield of wheat(Triticum Aestivum L.).The study investigated the effects of controlled-release urea in combination with normal urea on soil microbial conditions and wheat growth during critical period,and provided a theoretical basis and technical support for the application and promotion of controlled-release urea blended with normal urea in wheat.In this study,the responses of soil microbial diversity,wheat growth status and wheat yield in the soil were studied by using controlled-release urea blended with normal urea and only urea under wheat-maize rotation with straw returning for 7 years and 14 seasons.To investigate the distribution of soil microbial community,the change of soil nutrient status,the growth of wheat root system,the response of wheat yield and economic benefit under the treatments of controlled release urea and normal urea.16 S RNA high-throughput sequencing method was used to investigate the soil microbial status,and root morphology of wheat in 2018～2019 and2019～2020 seasons was observed and monitored by root scanning instrument.The results showed that:(1)Controlled-release urea blended with normal urea treatment under straw return increased the diversity of soil fungi and significantly increased the abundance of Pseudomonas,Bacillus,Humicola and other genera involved in cellulose and lignin degradation in the soil at the wheat filling stage compared to ordinary urea,which facilitated the steady and facilitated the steady and continuous degradation of the straw residue,thus promoting the synergistic process of both mineralization and humification;the inorganic nitrogen,total nitrogen and soil organic matter contents in the soil increased by 15.8%,7.5% and 11.6% respectively,providing more sufficient nutrients for wheat growth and improving the soil fertility status.(2)Controlled-release urea blended with urea treatment significantly promoted the growth of total root length,root surface area and total root volume by 57.6%,48.8% and 54.1% on average,respectively,at the two-year filling stage,improving the access to nutrients and water uptake of the wheat at soil depth.The advantage of nutrient supply from the controlled-release blended urea treatment promoted the above-ground growth of wheat,as shown that the controlled-release blended urea treatment significantly increased the plant height by 5.8%～12.6%and leaf area index by 25.2%～62.5%,which made wheat more favorable to receive light.During the critical growth period of wheat,the controlled-release blended urea treatment increased the net photosynthetic rate of wheat by 13.5%～22.2%,promoting the accumulation of dry matter.(3)Controlled-release urea blended with urea treatment significantly increased the amount of straw returned to the field and the above-ground biomass and N uptake of wheat,resulting in significant yield increases of 9.9%～46.8% and economic benefits of 11.6%～41.7% compared to the normal urea treatment.When the controlled release blended urea was applied at less than1/3 of the N applied to the regular treatment,it still maintained similar yields to the regular urea treatment.Although the cost of controlled release fertilizer was higher than that of ordinary urea,the use of controlled-release urea blended normal urea allowed for a single application,reducing the cost of fertilizers application labor while increasing the benefits from increased wheat yields.In conclusion,controlled-release urea blended with normal urea treatment with straw returning kept the soil C/N in a suitable and favorable range for soil microbial activity due to the rapid release of common urea in the early stages and the slow and sustained release of controlled-release nitrogen in the later stages,significantly increased the abundance of cellulose and lignin degrading microorganism,which was advantageous to the steady and continuous degradation of straw residue,thus promoting the mineral soil mineralization and humification processes.This also effectively increased the supply intensity and capacity of soil nutrients and promotes the process of wheat root growth and above-ground photosynthetic dry matter accumulation,ultimately leading to an increase in wheat yield and efficiency.Considering the actual management practices in the field,the application of straw in combination with controlled-release urea blended with normal urea achieve one-time simplified fertilization of crop and increased crop yield and efficiency,which was more in line with the goal of sustainable and intensive agricultural green development.