A Primary Study On Modeling Nitrogen Release From Cropland Organic Manures And The Model Regional Applications

Model establishment for simulating organic manures nitrogen dynamics is important to the management in the turnover of organic manures. Based on previous research, assuming that the C/N ratio of organic manures change as the decomposition proceeds and the change follows the first-order kinetics reaction, a dynamic model was developed to simulate the nitrogen release from organic manures. The model is described as â–³N_i =[N_i-1 ×△C_i -k×(R_i-1 -10)×N_i-1²]/C_i-1, where parameter k represents the first-orderkinetics constant of C/N variation velocity. In the model, â–³Ci represented the carbon transformation, it could be calculated by organic carbon simulation model. Fieldexperiment showed that, k was correlated with the initial C/N ratio(R₀) and the lignin content (L₀) of the organic manures: k = 0.0042× (R₀ /L₀) + 0.0015. The input of the modelcontains data of climate, soil character and parameters of organic manures.The model was validated against datasets from published literatures. The validation indicated that the model results in general agrees the datasets. The model had a preferably simulation effect on the process of nitrogen release from cropland organic manures.Jiangsu province was selected as the research region. Based on the data of climate, soil and crop production, the nitrogen releasing model combined with GIS was applied to analyse the spatial and temporal variability of nitrogen nutrition from organic manure. Next issues was discussed in this research: the essentiality of nitrogen nutrition from organic manures; spatial variability of nitrogen nutrition from organic manure in Jiangsu province; the variational trend of organic manure nitrogen nutrition from 1985 to 2000 and its causation; benefit with increased rate of straw incorporation and the status of straw incorporation in future.There were multifarious disadvantages to environment for the not reasonable usage to nitrogenous fertilizer. In this research the adequacy of the nitrogen application was evaluated by the models combined with GIS technique. At the basis of the soil mineralization model, organic manures nitrogen releasing model and nitrogenous fertilizer use efficiency model, the quantity of nitrogenous fertilizer that Jiangsu province cropland...