Effects Of Nitrate-n On Bioavailability Of Cadmium Under Different Water Managements

Three kinds of different water management methods,including irrigation,ammonium nitrate and nitrate nitrogen,were studied by using flood irrigation,dry and wet irrigation and wet irrigation in cadmium pollution?5 mg/kg?soil in this article.The effects of water and nitrogen regulation on the bioavailability of cadmium and the uptake and accumulation of cadmium were studied.The effects of plant height,tillering and root growth,organ biomass,yield and rhizosphere soil pH,available sulfur and microbial biomass Carbon,nitrogen,ammonium nitrate,nitrifying bacteria,nitrifying bacteria,iron redox bacteria,rice root iron and manganese film content for the safe production of rice to provide a scientific basis.The main conclusions are as follows:?1?Compared with flood irrigation,dry and wet irrigation was beneficial to the growth and yield of rice.The growth and yield of rice under the urea supply were the highest,while the growth and yield of rice under the supply of nitrate was the lowest.?2?Compared with flood irrigation,wet irrigation and dry and wet irrigation can improve soil available cadmium content and acid-soluble cadmium content,especially wet irrigation,and reduce the content of reducible and oxidizable cadmium.Compared with urea,the application of ammonium fertilizer can increase the soil available cadmium and acid soluble cadmium,while the application of nitrate nitrogen fertilizer can make soil available cadmium and acid soluble cadmium content decreased.?3?The content and accumulation of cadmium in the root and shoot organs of rice were: wet irrigation> dry and wet alternate irrigation> flood irrigation;compared with urea,ammonium nitrogen treatment significantly increased cadmium content in various parts of rice And the accumulation amount,nitrate nitrogen treatment significantly inhibited the absorption of cadmium in rice.Ammonium nitrogen and wet irrigation treatment significantly improved the uptake of cadmium by rice.?4?The soil p H was the highest and the effective sulfur content was the lowest in the rhizosphere soil,and the soil pH was the lowest and the effective sulfur content was the highest.The effective sulfur content of ammonium nitrogen treatment is higher than that of urea and nitrate.?5?Compared with flood irrigation and irrigated irrigation,wet and dry irrigation and wetirrigation could significantly increase the contents of soil microbial biomass C and N,among which the dry and wet irrigation was especially significant.The soil microbial biomass C,The highest content,while the lowest nitrate nitrogen treatment.?6?Effects of water management on soil ammonium nitrogen,nitrate nitrogen,rhizosphere soil ammoniated bacteria and nitrifying bacteria in rhizosphere soil of rice were: dry and wet irrigated> humid irrigation> flood irrigation;compared with urea Nitrogen content in soil was significantly decreased,but the content of NO₃-N was decreased,but the content of NO₃-N was significantly decreased.?7?With the increase of flooding degree,the Fe²⁺,Mn²⁺ and iron reducing bacteria adsorbed on the root membrane of rice increased significantly,and the growth rate of manganese adsorbed on rice root membrane was lower than that of iron.Nitrate treatment increased rice Number of Rhizosphere Iron Oxidation Bacteria and Ammonium Nitrogen Treatment to Increase Rhizosphere Iron Reducing Bacteria in Rice.Ammonium nitrogen treatment is helpful to the formation of rice root film.