Effects Of Urease/Nitrification Inhibitors On Nitrogen Cycle In Grassland Of Eergu’Na Soil And Their Applications In Environmental Protection Of Grassland

Grassland in northern China is a very important ecological barrier in China.It plays an important role in greening ecological environment,exporting favorable resources and ecological evolution sites.Due to global climate change and human factors,grassland in northern China is continuously deteriorated,causing many ecological and environmental problems.Nitrogen cycling and nitrogen fertility retention in grassland soil are the main limiting factors to play the important function of grassland ecosystem,while nitrogen cycle and nitrogen fertility retention capacity are closely related to the characteristics of soil organic nitrogen components and the enzyme activity related to mineralization turnover.The application of nitrogen fertilizer to grassland in China will soon become a common grassland management measure.However,the application of nitrogen fertilizer,especially the improper application of nitrogen fertilizer,will cause serious soil nitrogen loss,resulting in a series of environmental pollution such as low nitrogen utilization rate,groundwater pollution,eutrophication of the surrounding surface water and emission of N20 greenhouse gases.In recent years,urease inhibitor NBPT and nitrification inhibitor DMPP have attracted many scholars’ attention because they can effectively improve nitrogen use efficiency and slow down nitrogen loss.However,the effects of nitrogen and inhibitors on the soil nitrogen content,availability and the relationship with the activity of nitrogen mineralization turnover enzymes are important but lack.The topic of note.This paper,based on the Eergu’Na forest grassland ecosystem research station of the Shenyang Institute of Applied Ecology of the Chinese Academy of Sciences,uses a dual factor randomized block design to set up no fertilizer,urea(Urea),organic manure-cow dung(OM),1/2 urea +1/2 organic manure(1/2(U +O))and CK and urease inhibitors(NBPT:N-butyl thiosinphosphates).Acyl three amine),nitrification inhibitor(DMPP:two methyl pyrazole phosphate),urease inhibitor + nitrification inhibitor combination(N+D)were interactively added.The change characteristics of nitrogen components were studied by acid hydrolysis distillation method in the soil of 0-10cm soil layer,and the nitrogen related mineralization turnover was studied by spectrophotometer.The changes in enzyme activity(protease,amidase,urease and N-acetyl beta-D-glucosidase),and the relationship between nitrogen component and related mineralizing enzyme activity by redundancy analysis,in order to reveal the response characteristics of soil nitrogen component and nitrogen mineralization turnover enzyme activity to nitrogen fertilizer and inhibitor,as well as grassland soil in different periods.The potential mechanism of soil organic nitrogen turnover will provide a theoretical basis for exploring the effects of NBPT and DMPP and their two application on soil nitrogen cycling in northern China,providing technical reference and guidance for its application in grassland environmental protection.The main results obtained in this paper are as follows:1.in the forest steppe transitional zone in northern China,the long-term nitrogen input reduced the pH of the grassland soil,and the application of OM could effectively buffer soil acidification,and the N+D combination could also alleviate the acidification of soil.OM and 1/2(U+O)significantly increased soil microbial biomass C and N content,while Urea addition decreased their contents.NBPT and N+D significantly decreased microbial biomass carbon content,while DMPP increased microbial biomass carbon content.2.nitrogen addition significantly increased the content and proportion of soil amino acid nitrogen in two different periods.Plant growing period and green period of grassland,soil acid insoluble nitrogen content and significantly increased the proportion of.Nitrogen addition increased the content of hydrolytic total nitrogen and hydrolyzed ammonium nitrogen in the growing period of grassland plants,and the addition of inhibitors significantly reduced the content of unknown nitrogen in soil hydrolysis.The effect of NBPT and DMPP is related to the type of nitrogenous fertilizer.3.the addition of nitrogen fertilizer significantly increased the activity of protease and N-acetyl-beta-D-glucosidase in the grassland soil,and the effect of 1/2(U+O)was the most significant.Inhibitor addition significantly decreased protease activity and N-acetyl-beta-D-Glucosaminidase activity,and N+D inhibitor combination had the most significant effect.The addition of inhibitors significantly reduced soil urease activity,and NBPT had the best inhibitory effect on urease activity.In this experiment,N+D combination had no significant synergistic effect.4.the results of redundant analysis showed that the number of enzymes involved in nitrogen turnover in the green grassland was increased compared with the green grassland,and the interpretation of N-acetyl beta-D-glucosidase and amidase to organic nitrogen components increased significantly,and the explanation of protease to organic nitrogen components was less.Therefore,the potential turnover mechanism of organic nitrogen in grassland soil in different periods may be different.There are different kinds and different activity of nitrogen mineralizing enzymes involved in the mineralization turnover of organic nitrogen in different periods.The results showed that NBPT,DMPP and their combinations could effectively regulate the morphology and enzyme activity of the available nitrogen source under the different nitrogen addition conditions,thus affecting the nitrogen cycle of grassland and protecting the environmental nitrogen pollution of grassland.