Study On Mineralization---Immobilization Turnover(MIT)of Organic Fertilizer Nitrogen

Nitrogen (N) is often considered to be one of the most important limiting factors for plants. In arable and forage cropping, N fertilization application can improve the fertility of the soil and provide a sufficient N supply for plants. The research about organic nitrogen mineralization-immobilization turnover(MIT) is in a very active field. Pot experiments with isotopic tracer technique were carried out to study the dynamic of microbial biomass nitrogen and quick-acting nitrogen in soil and their sources after applied of N-fertilizer, N-fertilizer and wheat straw (W+F), N fertilizer and corn straw (C+F), N-fertilizer and hog manure, and only the hog manure, and to study the relations between the growth of corn and the amounts of micro-biomass and quick-acting nitrogen. The results were summarized as follows: 1 .When applied equal quantity of nitrogen, there was no difference between the N-fertilizer and organic nitrogen fertilizer on the growth of maize during the earlier stage of growing period. But after that, a deficiency was diagnosed except the application of N-fertilizer, and a more serious diagnosis was observed on the treatment of only application hog manure. So N-fertilizer application is needed when corn enter the period of maximum growth. 2.For C/N of hog manure is lower than that of straw, quick-acting nitrogen in soil of the treatment applied M+F was immobilized less than that applied C or W+F. It led to the maize growing better by the treatment applied M+F than that applied C+F and W+F. 3. NDFF% of maize was high during the earlier stage of growing period. With growth of the corn, 7NDFF% was lower than its in the earlier stage. But in the later, lots of soil micro-biomass nitrogen was mineralized and NDFF% was increased again. It proved that soil micro-biomass nitrogen can be used even it was immobilized and it is one kind of patterns to increase N-fertilizer efficiency. 4.Usually competition was exited between plants and soil microorganism, which was more dramatically when the nitrogen was not enough. The matter of nitrogen, energy, and the process of nitrogen turnover in soil control the intensity of the competition. Microorganism's compete ability was stronger than plant's when carbon and nitrogen was enough. As the process of soil nitrogen turnover was changed, the root of plant was intensive more and more, and stronger than microorganism's. The results of pot experiment showed that the amount of N offering by microbial biomass N occupied 96.2%- 156.3% of the amount of N uptaking by maize.