包膜尿素氮释放模拟与黑土简化施氮研究.

[Objective]The objective of this study is to investigate the possibility of single application of nitrogen fertilizer during the entire growing season of Maize through testing the characteristics of nitrogen release of both sulfur-coated and polymer-coated urea respectively under simulating and field conditions in situ. [ Method] In 2013 , both indoor simulating experiment and field experiment in situ were carried out, and only the field experiment in situ in 2014. Release-in-water method is used for indoor simulating and release-in-soil method in field with 94, 188 kg • hm-2N rates and single and double application ( pop-up at seeding and side-dressing at stem-elongation) methods resulting 7 treatments in total. Treatments were arranged in RGB with three replicates. Nitrogen rate was set at 156 kg • hm-2 and the number of treatments was 6 with 4 replicates in 2014. [ Result] The results showed that at 20 °C , the initial nitrogen release rate in water for SCU was bigger than 40. 00 % , and declined to 1.67 % /day in the 10 day middle period, while the lowest release rate of 0. 38 %/day was found in the 50 days long later period. Higher temperature increased the nitrogen release rate of SCU and shortened the release period. At 20 °C for the PCU in water release, four nitrogen release periods were distinguished as 0.30, 0.95, 0.45, andO. 14 %/day respectively. When the temperature was increased to 30 °C 9 the nitrogen release rate increased to 1.82 %/dav and the release period shortened from 155 to 44 days. Under the field conditions at 94, 188, 156 kg • hm-2 nitrogen rates, nitrogen release rate of single application of SCU was characterized by being higher in early stage and lower in later stage at 94 kg • hm-2 , while the double application method showed a relatively lower available nitrogen due to the split application at stem elongation. The nitrogen release model of both PCU and HUP (half urea plus half polymer-coated-u-rea) were comparable to that of double application of urea. [ Conclusion] It is concluded that both single application of PCU and single application could replace the conventional double nitrogen application method while the single application of SCU could not. [ABSTRACT FROM AUTHOR]