Dynamic Characteristics Of Nutrient Release And Prediction Of Release Rate And Longevity Of Controlled Release Fertilizer

In order to use the water incubation method results to predict the nutrient release of controlled release fertilizer in soil,nutrient release characteristics of 6 kinds of controlled release fertilizers in water and soil were studied.Then,the kinetic characteristics of nutrient release pattern were simulated by use of six dynamic equations.The optimal dynamic equation has been selected through statistics test.By use of the selected optimal dynamic equation,the regressive correlation equation of the release rate of the controlled release fertilizer in the water and soil was carried out.The correlation equation w ill be the prediction and forecast equations of nutrient releaese rate and longevity of the controlled release fertilizer in soil.The main findings and conclusions are as follows:1.Controlled release fertilizers have the same type of nutrient release pattern in soil and water.The nutrient release curve of PCU2?PMOP1 and PMOP2 is parabolic type.The nutrient release curve of PCU1?CRF and PDAP was"S"type.All showed that the nutrient release rate in the still water was faster than that in the soil,that is to say,the fertilizer efficiency longevity in still water is shorter than that in soil.2.In the soil with depth of 15cm and 30cm or of 5cm and 20cm,the accumulatio n nutrient release curve of the controlled release fertilizer is identical,the nutrient release rate was significantly positively correlated,and there was no difference in cumulative release rate.Show that it is indicated in the soil 15cm and 30cm or 5cm and 20cm,the depth of fertilization has no effect on the nutrient release of controlled release fertilizer.3.The nutrient release kinetics of controlled release urea,controlled release potash and controlled release compound fertilizer was best fitted with the Richards equation.The order of regression coefficients of the six fequations is the same in both soil and water.4.In the process of fitting Richards equation,in order to received the best equation,the maximum cumulative release rate,being parameter of N₀ had better to be the one calculated by statistical program during the simulation.When the N₀ value is set to 75%?reference to international convention?,80%?reference international standard?,and 100%?assuming full release?.The set N₀ value is closer to the N₀ value of the software fitting,higher,fitting degree of the equation.The set N₀ value of Controlled release urea and controlled release compound fertilizer were smaller in soil than in still water,but controlled release of potash is the reverse.N₀,d,k and ti values in depths of the soil 15cm and 30cm,5cm and 20cm were almost identical.5.Although the release rate of controlled release fertilizer in soil is less than that in water,there is a very significant linear correlation between those values and the r bing regression coefficient is very high from 0.9878 to 1.Therefore,the method of water incubation and its results can be used to predict nutrient release rate and longevity of the controlled release fertilizer in soil.