Simulation Research On The Nitrogen Transfer From Slow And Controlled Release Fertilizers

The characteristics of nitrogen release of inorganic coated fertilizers and poly-mer coated fertilzers were researched; the mathematical models of nitrogen release were built.The progress of the research on the subject was accounted, which was the transport of nitrogen from slow and controlled release fertilizers including release and migration. It was also introduced that the application of cellular automata in this field. Based on this account, the nitrogen release from slow and controlled release fertilizers and the nitrogen migration in soil solution were studied.The factors:temperature, vapour pressure and soil water content affected the nitrogen release of fertilizers. The vapour pressure difference between inside and ourside of the fertilizer coating layer was the essential reason of the nitrogen release. According to the Level1reaction kinetics equation, introduced the rate constant of nitrogen re lease-k and the activation energy of nitrogen release-Ea, built the dynamic model of nitrogen release, take2#-slow dissolve fertilizers and6#-polymer coated fertilizers as example, built a correlation equation, in view of the relationship between the accumulation release rate of nitrogen of fertilizers which was in soil and water. It provided a quick method for rapid determination nitrogen release rate in fields.The piecewise mathematical model of nitrogen release from inorganic coated fertilizers was built on the bases of Fick’s diffusion in porous medias.Where, the nitrogen release course was divided into two stage:the constant-release stage,0<t<t’; and the stage where is a gradual decay of release rate, t≥t’ The piecewise mathematical model of nitrogen release from polymer coated fertilizers was built on the bases of Fick’s second law, which using Laplace transform and leave number theory.Where, the nitrogen release course was divided into three stage:(1) lag period, t≤t’, the initial stage during which almost no release is observed,(2) the constant-release stage, t’<t≤t" and (3) the stage where there is a gradual decay of release rate,t>t". This three stage approach gives a good description of the release course for polymer-coated fertiliser. Adopting this three stages of release, the purpose of the paper is to develop a model that can adequately represent nitrogen release from polymer-coated fertilisers.In contrast to the continuity ideal hypothesis of mathematical model, the cellular automata’s discrete analog can simulate the nitrogen release from fertilizers more really. The structure materials of slow and controlled release fertilizers were expressed by matrix element, and the nitrogen release course was studied by simple cellular automata evolution rules. Neumann neighbor condition was adopted, and the evolution probability was determined by the secondary distribution theorem of probability theory. The accumulate release rate of nitrogen could be described by the percentage of accumulated evolution cell. The results indicated that the cellular automata can simulate the release of slow and controlled release fertilizers and explain the phenomena during the release process. The accumulated amount of release or release ratio can be fitted by the percentage of accumulated evolution cell. This2d cellular automata model realized dynamic visual simulation of nitrogen release from fertilizers successfully. The compare was made according to the theoretical basis and the applicable scope, which was used to study the characteristics of nitrogen release from fertilizers which was simulated by mathematical model and cellular automata model. The results showed that the mathematical model always has a certain error for its theoretical basis hypothesis was different from the actual circumstance of fertilzier nutrient release. Well, the cellular automata model were more accord with fertilizer nutrient release process for its’discrete properties.On the basis of the solute transport theory in soil, the dynamic water-still water districts model was simplified, the nitrogen transport process in soil solute was idealized as solute diffused in porous media. The cellular automata model was established to study this process. The results indicated that the cellular automata model can simulate the migration process of nitrogen, it provided a new means for research the solute transport in soil.