Effects Of Natural Grass On The Orientation And Transformation Of Exogenous Nitrogen In Different Forms In Apple Orchard

Nitrogen is one of the most important elements in apple’s growth and developmentt.Nitrogen content and absorption and utilization affect the yield and quality of orchards in a large part.Nitrogen can be absorbed and utilized by fruit trees mainly exists in three forms,named amide nitrogen,ammonium nitrogen and nitrate nitrogen.Under the influence of physiological characteristics,climatic environment and soil conditions,plants have significantly different nitrogen requirements in different stages of growth and development.In this study,under the background of orchards in cold and cool climate zone,nitrogen morphology was used as a starting point to compare and contrast the absorption,utilization and loss of different nitrogen forms of cold-rich seedlings under the condition of conventional tillage and natural grass,which was of great significance for improving the utilization rate of nitrogen fertilization and solving the pollution which is caused by excessive nitrogen fertilizer application.1.The absorption,utilization,distribution and loss of ¹⁵ N in the Malus domesticaseedlings after the application of amide nitrogen（CO（NH2）2-N）,ammonium nitrogen（NH4+-N）and nitrate nitrogen（NO3--N）were studied by applying the ¹⁵ N isotope tracer technique in natural grass and conventional tillage condition.The results showed that under the condition of conventional tillage,the highest utilization rate of ¹⁵ N of the Malus domesticaseedlings under different nitrogen treatments for three months and one year was ammonium nitrogen treatment.Under the condition of the natural grass,different forms of nitrogen treatment for three months and a year of ¹⁵ N utilization size order of NO3--N,CO（NH2）2-N,NH4+-N,two processing cold rich seedling utilization ratio under nitrate ratio as high as 27.57% and 37.03%.Compared with the increase of amplitude of utilization rate under the same nitrogen treatment from 3 months to 1 year,found that the increase of amplitude of NO3--N treatment is the biggest,it means that natural grass can significantly reduce the loss of NO3--N.From the perspective of Ndff value,the ¹⁵ N regulation ability of the leaves of the Malus domesticaseedlings treated with nitrate under the condition of natural grass was significantly improved compared with the leaves treated with nitrate nitrogen under the condition of conventional tillage.2.Under the condition of natural grass,the activities of key enzymes of nitrogen metabolism in the leaves and roots of the Malus domestica seedlings were significantly different after treatment with different forms of nitrogen,and the nitrate reductase activity in leaves was the highest treatment through the three nitrogen,which was significantly higher than the NR activity in the leaves after treatment with other forms of nitrogen under the condition of natural grass.3.Under the condition of natural grass,different forms of nitrogen in soil nutrients shows that under the same form of nitrogen treatment,compared to the treatment under conventional tillage condition,natural grass significantly improved the 0cm³0cmsoil the content of soil organic matter and other mineral nutrients,sward under the processing conditions of nitrogen form 0cm³0cm soil microbial carbon,nitrogen contents was significantly higher than that of conventional tillage condition of these forms of nitrogen treatment of soil microbial biomass carbon,nitrogen,and under the condition of the sward,the solid in 0cm³0cm under different forms of nitrogen treatment had no significant difference between soil microbial biomass carbon content.