研究尿素（U）为肥芯、鸟粪石（S）和生物炭（B）为包膜材料制备的缓释尿素氮磷释放特征对评价其农用具有意义。采用静水培养和土柱间歇淋溶试验，分析5种处理（CK、U、S包膜尿素（USR）、S+低比例B包膜尿素（USB1R）和S+高比例B包膜尿素（USB2R））水中和土壤淋溶液中TN、TP、NH4+-N、NO3--N和PO43-，研究肥料氮磷缓释特征。结果表明，缓释肥在静水中（25 ℃）24 h和28 d氮释放速率分别≤15%和≤80%，符合缓释肥标准（GB/T 23348—2009）。缓释肥料在土壤中前7 d氮磷释放速率快，随后逐渐下降；其在土壤中磷释放速率：USB1R （50.9%） > USB2R （38.3%） > USR （10.0%），氮释放速率：USB2R （86.2%） > USB1R （83.1%） > USR （74.0%）；缓释肥氮释放速率比尿素低9~21百分点。可见，鸟粪石及生物炭包膜尿素氮磷具有缓释性，其实际肥效有待进一步验证。
The characteristics of nitrogen (N) and phosphorus (P) release from slow-release urea, developed based on urea (U) as fertilizer core and struvite (S) and biochar (B) as coating materials, are significant for evaluating the application of high N and low P fertilizer in agriculture system. In the present study, the hydrostatic test and soil column intermittent leaching experiment including five treatments (CK, U, S coated urea (USR), S+low proportion of B coated urea (USB1R), S+high proportion of B coated urea (USB2R)) were carried out to investigate the N and P release from individual S coated U and S combined with B coated U in calcareous soil based on analysis of TN, TP, NH4+-N, NO3--N, and PO43-. The results showed that release rate of N in slow-release fertilizers based on hydrostatic test was not higher than 15% within 24 h and 80% within 28 d, which meets the standards of the slow-release fertilizer (GB/T 23348—2009). The release rates of N and P in the three slow-release fertilizers swiftly increased in soil for the first 7 days, and then gradually decreased. The release rates of P in the three slow-release fertilizers were in the decreasing order: USB1R (50.9%) > USB2R (38.3%) > USR (10.0%), and the release rates of N were in the order: USB2R (86.2%) > USB1R (83.1%) > USR (74.0%). The release rates of N in slow-release fertilizers were lower by 9-21 percentages than that in urea. The individual S coated urea and S combined with B coated urea showed slow release of N and P in calcareous soil. The actual efficacy of the developed slow-release fertilizers needs to be further verified.
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