Assessment of changes of fertilizer nutrient in soil by ion exchange resin membrane method

Ion Exchange Resin Membrane(IERM) method was adopted to study the changes of three nutrients(N, P and K) from four fertilizers(urea, potassium chloride, calcium phosphate and slow-release-compound fertilizer) in a continuous soil incubation experiment at 25℃. The results showed that there was significant disparity of nutrient release rate in four fertilizers. The release rate of N and P in slow-release-compound fertilizer was slower than others at the prior stage(28 days). The release accumulation of nutrients(N, P and K) in soil was enhanced gradually with time and could be quantitatively described by four kinetics equations: Elovich equation, double constants equation, primary diffusion equation and parabola diffusion equation(r=0.863^**-0.999^**). The change characteristics of fertilizer nutrients in soil determined by IERM were similar to the corresponding nutrients changes in soil itself by the same method. Therefore IERM may be considered as a better method to evaluate the changes characteristics of fertilizer nutrient in soil.