Effects Of Controlled-Release Urea On Ammonia Volatilization And Nitrogen Residual And Balance In Corn Farmland

The region of Huang-Huai-Hai is an important food region in China, however, in this region, the nitrogen fertilizers were used excessively and the nitrogen use efficiency was low in agricultural production. This field experiment and indoor chemical analyses were conducted to evaluate the effect of controlled-release urea coated by sulfur or polymer on soil ammonia volatilization, nitrogen balance, corn growth and yield. The results can provide theoretical supports for the application of controlled-release urea and the development of sustainable agriculture. Main results were summarized as follows:1. During the maize growth season, compared with common urea, the controlled-release urea fertilizers lowered the accumulated loss amounts of soil ammonia volatilization by 6.51-9.92 kg·hm^-2; delayed the period for reaching the soil ammonia volatilization flux peaks with 4–5 days. When using the two controlled-release urea fertilizers, the time ammonia volatilization flux (67 days) and the ammonia loss rates were reduced by 0.09-0.15 kg·hm^-2·d-1and 2.76%-3.51%, compared with the common area fertilizer. The controlled-release urea fertilizer coated with polymer was found to have more desirable properties than the fertilizer coated with sulfur.2. The controlled-release urea reduced the potential nitrogen loss leaching to the deeper soil layer. The controlled-release urea coated by sulfur or polymer effectively controlled the release of nitrogen at the early period of maize growth and guaranteed the supply of nitrogen at later stages. As a result, this urea released nitrogen smoothly, well controlled the migration of nitrogen downward, reduced the waste of nitrogen resources and reduced the environmental pollution of excessive nitrogen for farmland.3. The controlled-release urea maintained the content of NH₄⁺-N, NO₃^--N in high level and further kept the level of nitrogen fertility in topsoil. In addition, the controlled-release urea coated by polymer had a better performance than the urea coated by sulfur.4. The controlled-release urea significantly increased the growing indexes, the yield of corn, grain quality and nitrogen use efficiency. Comparing with common urea, the controlled- release urea increased the maize yield, nitrogen use efficiency and agronomic use efficiency by 14.61%-37.50%, 12.38%^-20.87%, 4.79%-9.38%, respectively, and decreased soil nitrogen dependent rate by 8.87%^-13.58%. The controlled-release urea coated by polymer had the highest fertilizer contribution rate.5. According to the calculated nitrogen balance in soil-crop system during maize growth period, the controlled-release urea improved nitrogen use efficiency, reduced the content of residual inorganic nitrogen after harvesting and reduced the loss of nitrogen. Comparing with common urea, the controlled-release urea significantly increased the content of nitrogen taken out by crop by 6.83%^-27.39% and reduced nitrogen apparent loss of corn nitrogen to 4.59-43.84 kg·hm^-2, respectively. The controlled-release urea had a high ecological effect and application value.