Development of control release urea fertilizer model for water and nitrogen movement in flooded rice

Application of control release fertilizer in rice cultivation is a smart way to reduce the environmental nitrogen contamination and enhance the nitrogen use efficiency. The effect of coating thickness and radius of urea granule on nitrogen release rate was modelled, but their effect on nitrogen transformation in soil was not modelled for any crop. In this study, a simple rice water and nitrogen balance model was integrated with a nitrogen release rate model and the effect of coated urea on nitrogen transformations was studied in the CRF-applied flooded rice. The simulated nitrogen release during urea hydrolysis was verified with literature data for uncoated, polymer-coated and mix urea (polymer-coated + uncoated) cases. The integrated model successfully predicted the lag, linear and decay periods of nitrogen release, and peak nitrogen concentration during urea hydrolysis and declining trend during nitrogen transformations. The integrated model could be used as a management tool for determining optimum coating thickness and urea radius for which the nitrogen loss to environment is minimum.