Model Establishment For Simulation Cropland Nitrogen Supply

Organic nitrogen in soil can be divided into labile and recalcitrant fraction. Assuming that mineralization of nitrogen in soils follows the first-order kineticsreaction. The model was represented by a differential equation of It's integral and difference equation can be induced and we choose preferable one. The process of fertilizer supply nitrogenfollows first-order kinetics too, it can be expressed as . Soiltemperature and soil water status influence the kinetics constant. Potential providing nitrogen was expressed as product of nitrogen and it's use efficiency. The maximum nitrogen of crop intake is the sum of both.Soil nitrogen mineralization is the process of microbio's bio-chemi reaction, the intension and quantity depend on not only soil's organic matter, but also temperature and moist. Field experiment simulation is the final purpose. The result is strongly infected by temperature and moist, so they are the sticking point of mineralization parameter. Crop intake nitrogen as factual value, we adjust temperature and moist to quantitative analysis the nitrogen supply.Previous model was validated by experimental and collected data from other authors. Model simulation in general agreed with the measurement. Rice process, Rice yield and wheat process comparison between computed and measured in linear correlation coefficients r values of 0.96***(n=233), 0.87***(n=47), 0.80***(n=100)o According to the model simulation, most region was in short of nitrogen nutrition.By analyzing a total of 385 field measurements conducted in China over the last 15-year period, the authors developed a statistical model for quantifying the dependence of nitrogen use efficiency (NUE) on nitrogen application rate (Ninput, kg/ha) for rice and wheat crops, which is described as NUE=144.1 X Ninput-0.2(R2=0.627, P<0.001) . Model analysis indicates that there is a regional difference in the NUE. The NUE in developed region (e.g., Jiangsu Province) is lower than that in undeveloped region (e.g., Heilongjiang Province).Model is sensitive to temperature and moist, alter any of them will great change the nitrogen supply. Environmental factor can great change soil nitrogen supply in whole crop growth season. To fertilizer nitrogen supply, it is different in inundation rice and dry wheat field. It is necessary to distinguish between nitrogen supply process and result.