N-releasing characteristics of different kinds of controlled-release urea and their effects on the sugarcane

The present experiment was undertaken in order to study the N-releasing characteristics of different kinds of controlled-release urea and their effects on the sugarcane.Five treatments,viz.CK,normal urea,resin coated urea,sulfur coated urea and the mixture of the coated urea have been applied in the sugarcane field,and the fertilizer packages were buried into field at the same time.The result showed that the Elovich equation could fit the process of N releasing from resin coated urea with good results(r=0.9796**-0.9944**).It was found more N was released at the early stage,and less at a later stage.However,the wax/resin coated urea could make up the deficiency of resin coated urea.The process of N release from sulfur coated urea could be well fitted by the parabolic diffusion equation(r=0.9914**-0.9973**).The sulfur coated urea released N stably,but hardly met the requirement of sugarcane growth at the early stage.Compared with the common urea,the controlled-release urea has increased the sugarcane yield and nitrogen utilization efficiency by 5.0-11.4% and 7.5-8.2%,respectively.The different kinds of coated urea should be mixed in proper proportion in relation to the N-releasing characteristics of different controlled-release urea and the needs of sugarcane for fertilizers.It could realize balance between supply and demand for nutrient and improve the utilization efficiency of controlled-release fertilizers.