Effect of Water Vapor Pressure and Soil Moisture on Nutrient Release Characteristic of Chitosan Coated Urea

Experiments for nutrient release of chitosan coated urea(CCU) were carried out to elucidate the effect of moisture on nutrient release characteristic of CCU.Results showed that,CCU is a good slow-release fertilizer.The nutrient release is linearly related to the water vapor pressure and depends on the ion concentration of liquid medium.The cumulative nutrient release can not reach 100% in the saturated salt solution.The release of CCU is attributed to the cumulative effect of particles that each release(nutrient) individually at a different time,since individual granule is unable to release urea sufficient for the demand.Increasing the water capacity of soils leads to the increase of the nutrient release rate.The effect of soil moisture on the CCU nutrient release is very complex, and could not be forecast by the model developed on the basis of the experimental results in water saturation.In drought soil,CCU has a better nutrient release characteristic than polymer coated urea.