Nitrogen release characteristics of different hermetic material sulfur coated urea and their effects on summer maize

The trials of nutrient release characteristics of different sulfur coated urea which coated with paraffin (SCUA) and urea formaldehyde colophony (SCUB) were studied by water extraction and soil incubation methods. At the same time, a field experiment was conducted to study the effects of SCUA and SCUB on plant growth, yield, nitrogen utilization efficiency and net benefits of summer maize, and the soil residual nitrate nitrogen. The results show that the nitrogen release curves of SCUA and SCUB are linear relationships with the time，and the nitrogen release rate is under the national chemical industry standard of SCU（Ⅰtypes）. The nitrogen released rates of SCUA and SCUB in water are faster than those of buried in the field for the different environmental conditions. And the releasing rate of SCUA was higher than that of the SCUB. The cost of SCUB decreases 49.39 yuan/t compared to the SCUA. There are no significant differences in growth and yield among the treatments of SCU (SCUAJ and SCUBJ) which nitrogen application rates are 70% of custom dose and treatment of common urea with custom dose. The treatments of SCUAJ and SCUBJ could significantly improve apparent nitrogen utilization efficiency which can reach to 40.45% and 42.59% respectively. The residual nitrate nitrogen contents of CK1(common urea with custom dose )and CK2 (nitrogen application rate was70% of custom dose) in 60-100 cm depth of soil are higher than those of other SCU treatments after harvest. There are no significant differences in net benefits of the SCUA and SCUB with the same rate and there are no net benefit differences compared to the conventional one even under a 30% rate application reducing condition. Therefore, it can be speculated that urea formaldehyde colophony can be used in SCU production as hermetic material, and thus benefit to cost-saving and profit-increasing.