| In China the utilized rate of nitrogen fertilizer in one season is only about 30%.At present,urea is the most widely used nitrogen fertilizer variety in agricultural production.The low utilization rate of nitrogen fertilizer not only causes waste of resources,but also causes soil and environmental pollution,seriously endangering the agricultural ecosystem.Amino acid has been widely used as a fertilizer value-enhanced substance.Soil microorganism is the most active part of soil ecosystem,and it also reflect nutrient bioavailability.The application of different forms of nitrogen fertilizer can significantly change the types and abundance of soil microorganisms,and the response of different microorganisms to nitrogen fertilizer leads to different soil nitrogen utilization efficiency.In this study,a new type of value-enhanced urea product was created by combining amino acid with urea.The effect of the amino acid enhanced urea on the rhizosphere nutrients and rice growth was explored by indoor pot experiment under straw and flooding cropping system.The purpose of this study is to provide basis for urea application in rice.There are six treatments in the experiment,namely: dry farming without nitrogen application(GCK),dry farming general urea(GU),dry farming amino acid value-added urea(GAU),water farming without nitrogen application(SCK),water farming general urea(SU)and water as amino acid value-added urea(SAU),all the treated phosphorus and potassium fertilizers are applied in equal amounts at one time.The results are as follows:1.Compared with the common urea(U),amino acid enhanced urea(AU)promoted root growth,and promoted the fresh weight of roots by 9.65% and 7.56% respectively in straw and flooding cropping;in straw cropping system,the root length,root diameter,root surface area and root tip number increased by 45.06%,25.93%,6.17% and 90.52%respectively;in flooding cropping mode,the root growth of GAU was also increased,but the increase was decreased and the same of nitrogen fertilizer;the root length,root diameter,root surface area and number of root tips in straw condition were significantly lower than those in flooding,which were 26.20%,15.63%,2.52% and 13.95% lower in the treatment of GU than those in SU treatment.While the reduction of the treatment of GAU was significantly lower than the treatment of SAU.2.Comparing with the treatment of GU,the organic carbon,total nitrogen and microbial nitrogen of treatment GAU increased by 17.04%,18.20%,30.00%,respectively,while comparing with the treatment of SU,the ammonium nitrogen and microbial nitrogen of treatment SAU increased by 39.70% and 38.01% respectively,whereas the nitrate nitrogen decreased by 33.70%.Compared the treatment of GU and SU,the total number of bacteria in the treatment of GAU and SAU increased 1.70 and 1.90 times(P < 0.05)and the number of ammonifying bacteria and nitrifying bacteria increased 1.52 to 2.67 times in two rice cropping modes.3.The overall study found that,compared with ordinary urea,amino acid value-added urea treatment significantly improved the richness and uniformity of the soil microbial community.The AWCD values of soil microorganisms in each treatment are: SAU>GAU> SU>GU>SCK>GCK.The overall change is that with the sampling time extending,it increases rapidly first,then increases slowly after 96 h,and reaches the maximum value at 192 h.Further analysis of the 96-hour AWCD value under different treatments reveals that the AWCD value of amino acid-value-added urea treatment is higher than that of ordinary urea An increase of 27.35%(aquatic)and 19.04%(aerobic)indicates that the application of amino acid urea under water has a more significant effect on microorganisms.4.The dominant population of bacterial in the rhizosphere of rice root was Sphingomonas,the relative abundance was 18.78% ～ 22.59%.The dominant population was Aeromonas and Flavobacterium,with a relative abundance of 43.09%-52.72% and14.86%-18.87% respectively.Compared with urea treatment,Aeromonas and Sphingomonas in the AU decreased significantly,while uncultured bacterium C-subgroup-6 increased significantly.The total nitrogen,ammonium nitrogen and organic carbon contents were significantly correlated with microbial community structure.5.Amino acid added urea changed the metabolism preference of soil microbial community to alcohol,acid,amino acid,lipid and amine carbon sources,and significantly improved the utilization ratio of six carbon sources compared with common urea.The results of principal component analysis showed that alcohols and amines were the main carbon sources which caused the differences of soil microbial community metabolism characteristics under different nitrogen treatments.6.Under water and dry cultivation,the addition of amino acid increment agent mainly affects the bacterial community structure by affecting the amount of soil ammonium nitrogen.There was a significant correlation between the content of ammonium nitrogen and the content of soil total carbon,total nitrogen and soil ammonifying bacteria,and a significant correlation between the content of nitrate nitrogen and soil nitrifying bacteria.The results showed that the addition of amino acid value-added agent mainly affected the rhizosphere microbial process of soil carbon and nitrogen transformation by affecting the content of soil ammonium nitrogen.The results showed that the application of amino acid value-added urea significantly promoted root growth and root morphology formation in the early stage of rice growth,increased rhizosphere biomass carbon and nitrogen,reduced the nitrate nitrogen content in the rhizosphere of water cultivation,increased the ammonium nitrogen content,stimulated the rhizosphere bacterial population breeding,increased the diversity of Rhizosphere bacterial colonies,and was conducive to rice nitrogen absorption and soil nitrogen conservation. |
