Effects Of Controlled Release Nitrogen Fertilizer Combined With Urea On Soil Nitrogen And Soil Microorganism Changes

In agricultural production,in order to increase the yield per unit area,the phenomenon of multiple fertilization and massive nitrogen application is widespread.This not only increases the cost of production,but also makes soil acidification,greenhouse effect and water eutrophication more serious.Controlled release nitrogen fertilizer can extend the nitrogen supply cycle,and has obvious effect on crop growth and production.However,its high cost and insufficient early nitrogen supply limit its popularization and application.Therefore,it is necessary to discuss the rational ratio of the one-time fertilization of the controlled release nitrogen fertilizer and the urea,and to reduce the production input and achieve the environmental protection and efficiency of production without reducing the yield.Previous studies tended to focus on increasing crop yields and improving nitrogen use efficiency,there are few studies on nitrogen transformation process and microorganism driving mechanism in the soil,so it is difficult to reveal the internal mechanism of high efficiency utilization of nitrogen.In this study,a pot experiment of rice and wheat was conducted to combine controlled release nitrogen fertilizer with urea in different proportions,through studying soil nitrogen transformation and supply process and microbial changes,analyzing the reasons,screening the best proportion of application,and providing basis and reference for its popularization and application.The main results are as follows:?1?The soil inorganic nitrogen supply at the tillering stage of rice and wheat was the fastest treated with single urea treatment,and gradually slowed down with the increase in the proportion of controlled release nitrogen fertilizer,and it was more suitable to apply20%⁸0%controlled release nitrogen fertilizer.From the jointing period to the mature period,in wheat season,soil ammonium nitrogen and nitrate nitrogen were significantly higher than single application urea treatment under the treatment of 20%¹00%and40%¹00%controlled release nitrogen fertilizer,which increased 0.53¹.38 mg·kg^-1and12.77³9.60 mg·kg^-1respectively,and 40%controlled release nitrogen fertilizer treatment is the best.The treatment of 40%¹00%controlled release nitrogen fertilizer could significantly increase the content of ammonium nitrogen and nitrate nitrogen in rice,and increased 1.41⁴.21 mg·kg^-1and 0.95¹.81 mg·kg^-1compared with single application urea treatment,and the inorganic nitrogen supply was the most abundant with 40%controlled release nitrogen fertilizer.?2?The number of soil microorganisms in the tiller stage of rice wheat treated with20%¹00%controlled-release nitrogen fertilizer was lower than that of single urea treatment,tut there was no significant difference.With the growth period,the number of soil bacteria,actinomycetes and fungi in wheat soil was more abundant with 40%,40%⁸0%and 20%⁴0%controlled release nitrogen fertilizer,which was significantly higher than single application urea treatment.In the rice season,the amount of bacteria,actinomycetes and fungi increased significantly by applying 40%,20%⁴0%and40%⁸0%controlled release nitrogen fertilizer respectively.The number of soil microorganisms was most controlled by 40%controlled-release nitrogen fertilizer.Among the nitrogen conversion bacteria,the treatment of 40%¹00%controlled release nitrogen fertilizer could improve the soil ammonification and nitrifying bacteria in the middle and late growth of rice and wheat.Soil denitrifying bacteria were treated with 80%¹00%controlled-release nitrogen fertilizer most,the difference between booting stage and mature stage was obvious.?3?Nitrogen supply in rice and wheat during tillering stage was too fast under single urea treatment,and the ammonification,nitrification and denitrification intensity were the strongest in soil.The 40%¹00%controlled release nitrogen fertilizer was suitable for nitrogen transformation and nitrogen supply was stable,denitrification was significantly lower than single application urea treatment.From the jointing stage to the mature period,the treatment of 40%¹00%controlled release nitrogen fertilizer significantly improved the soil ammoniation strength of rice and wheat,while the nitrification intensity was better with the treatment of 20%¹00%controlled release nitrogen fertilizer,which was significantly higher than the single application urea treatment.However,there was an excess of nitrogen supply in the later stage of 80%¹00%controlled release nitrogen treatment,the denitrification intensity of rice and wheat from booting to maturity was significantly higher than that of other treatments,which is easy to cause nitrogen loss.Effects of different treatments on soil nitrogen transformation and supply,microbial biomass and nitrogen transformation functional bacteria in rice and wheat in two seasons were comprehensively considered,the results showed that 40%controlled-release nitrogen fertilizer combined with 60%urea treatment had the best effect.The treatment can regulate nitrogen release rate reasonably,promote the growth of soil microorganism,and the nitrogen transformation intensity could better meet the needs of nitrogen nutrition in different growth stages of rice and wheat.