| Nitrogen is the primary limiting factor for maize production and the largest amount of nutrients that needed. Unreasonable application of nitrogen will result in low NUE, too much residual nitrate in soil and agricultural non-point source pollution and other issues of concern. Appling slow/controlled release fertilizers brought new ideas to solve above problems. In theory, slow/controlled release nitrogen have the potential to control N release rate, and meet crops need during the growth period by a single application. However, in the actual application process, there is inconsistent between laboratory and field measurement data for nutrient release rate of controlled release urea. It is instability for application effect of controlled release urea in different regions and crops.This study focused on the problems of controlled release fertilizer nutrient release measurement and effect in practical application process, with in the method of laboratory and field trials. Searching for(1) Nitrogen release characteristics of two coated urea;(2) Effect of coated urea on nitrogen accumulation, dry matter weight, yield and NUE of maize;(3) Effect of coated urea on soil inorganic nitrogen content. This study try to search for the relationship between lab and field measuring methods of coated urea nutrient release rate, comprehensive evaluate the application effect of two coated urea. The results showed that:Nutrient release characteristics of two coated urea are significantly different. The release curve of resin coated urea was similar to the "S" shape. Nutrient release characteristics could be described using the first-order kinetics equation. Temperature and media were two factors affecting nutrient release rate of resin coated urea. Temperature was significantly positively correlated with nutrient release rate and inversely correlated with stated release time.Soil medium can significantly accelerate the nutrient release rate and shorten the stated release time of resin coated urea compared to water medium. Stated release time of resin coated urea was 88 days in water medium at 25℃, was 54 days in field soil medium. There was a certain relationship between two measuring methods of stated release time, the latter(X) of stated release time can be fitted by the former(Y), the regression equation was Y = 0.000088X3- 0.0187X2 + 1.3737 X + 17.117. The release curve of sulfur-coated urea was similar to the parabolic shape. Nutrient release characteristics could be described using quadratic in condition of lab experiment. The nutrient release trend of sulfur-coated urea was significant affected by media for water and soil, slight effect by temperature. Stated release time of sulfur-coated urea was 42 days in lab soil medium at 25℃, was 33 days in field soil medium. Relationship between the two stated release time was fitted the equation: Y = 0.00016X3- 0.0105X2 + 0.7574 X + 5.0334.In 187.5kg/hm2 N, sulfur-coated urea exerting high initial release(burst effect).This inflicted damage to young maize seedlings and nitrogen accumulation,dry matter at different growth stages,yield, NUE was reduced in comparison to urea and resin coated urea treatments. On the contrary, resin coated urea got the heaviest yield 11276.04kg/hm2. It was increased by 6.31% and 20.00% compared with urea and sulfur-coated urea, respectively. Nitrogen use efficiency(RE) of resin coated urea was 35%, which was 11% higher than sulfur-coated urea treatment. In 93.75kg/hm2 N, The order of nitrogen accumulation, dry matter, yield, nitrogen use efficiency were resin coated urea > sulfur-coated urea > urea. Resin coated urea treatment yield was 10345.86kg/hm2 and highest among these treatments, nitrogen use efficiency(RE) was 51%.From jointing to maturity, nitrate content of each soil layers and topsoil inorganic nitrogen accumulation was gradually decreased. The inorganic and nitrate nitrogen of nitrogen fertilizer treatments were higher than that without N application. From jointing to maturity, the rang of inorganic nitrogen content in the topsoil of high urea rate treatment was biggest, decreased from 159.33kg/hm2 to 36.55kg/hm2; the rang of inorganic nitrogen content in the topsoil of high resin coated urea rate treatment was smallest, decreased from 68.95kg/hm2 to 57.02kg/hm2. Resin coated urea maintained inorganic nitrogen content of topsoil at a high level, which was important for maize to obtain high yield.Comprehensive analysis of the nutrient release characteristics, biological effect, economic effect and environmental effect of resin coated urea and sulfur-coated urea, the application effect of resin coated urea is better than sulfur-coated urea. "S" shaped nutrient release curve of the resin coated urea could meet the crops nutrient needed, and got a highest yield and economic benefit and could significantly improve NUE. Due to the influence of membrane integrity, sulfur-coated urea released excessive nutrients at beginning. It was resulted in damage to maize seedlings and lowest yield, economic benefit under high sulfur-coated urea treatment. The application effect of low sulfur-coated urea treatment between urea and resin coated urea. |
PDF Full Text Request