Characteristics Of Nitrogen Release And Effect On Environment Of Different Kinds Of Coated Urea

The nitrogen releasing characteristics of coated urea produced in Japan (LP40, LPS40, SC60, LPSS and LPSS 100) was studied through purified water culture under the same temperature, which was fitted with the first-order reaction model, and microstructure of membranes of coated urea before and after purified water culture was characterized by a scanning electron microscopy (SEM). And then a rice pot experiment was conducted with three kinds of coated urea that have significant difference of nitrogen releasing characteristics (LP40, SC60, LPSS), self-made coated urea (BB) and common urea (UR). We investigated the effect of different kinds of coated urea on NH3, NOX, CO2 emissions, NH4+-N, NO2--N, NO3--N content in soil leachate, rice growth and nitrogen use efficiency during the different growth stages of rice. Variety of soil nutrients also was studied after rice harvest. Research results as follows:1. The nitrogen releasing characteristics could be described by the first-order reaction model. Equation parameters k was the nitrogen releasing rate constant, which was in proportion with nitrogen releasing rate and inverse the days of the 50 percent of nitrogen releasing rate. The outer surface intergrity of LPSS, SC60 were better than LP40, and the water resistance of LPSS membrane was much better than others because of the compactness of the cross section membrane analyzed by SEM.2. Compared with common urea (UR), coated urea had a inhibit effect on NH3, NOX, CO2 emissions in paddy soil during rice growth stages. Coated urea of LP40, LPSS, BB, SC60 could decrease the NH3, NOx, CO2 emissions for 5.4%-19.3%,8.1%～23.4%, 1.6%-13.0%, respectively.3. Compared with common urea (UR), nitrogen content of LP40, LPSS, SC60 in soil leachate reduced 58.27%,46.38%,33.30% during rice growth stages, respectively.4. Compared with common urea, under the same nitrogen level, coated urea could promote rice growth, increase rice chlorophyll content, rice yield and nitrogen use efficiency. pH of surface soil, nitrate nitrogen, ammonium nitrogen and alkaline hydrolysis content also increased.Above all, coated urea could inhibit NH3, NOx, CO2 emissions in paddy soil, reduce nitrogen (NH4+-N, NO2--N, NO3--N) leaching losses, increase soil nutrient content, promote rice growth and improve nitrogen use efficiency.