几种聚氨酯包膜尿素的氮素释放特征研究

以聚氨酯为主要包膜材料，以石蜡、改性高岭土和双氰胺(氧化钙)为组合材料，采用滚转包衣法制备了3种聚氨酯包膜尿素。通过静水浸泡和盆栽试验，探讨了3种自研制聚氨酯包膜尿素的氮素释放特性，在氮磷钾等养分供应下研究了6个施肥处理对春玉米生长发育和氮素吸收利用的影响。结果表明，3种自研制聚氨酯包膜尿素在静水(25℃)中氮素累积释放比例的变化趋势基本一致，其24 h 初期释放率为2.04％~3.64％(≤15％)，28 d累积释放率为29.88％~34.80％(≤80％)，符合缓释肥料的国家标准要求。相对于NPK处理，自研制聚氨酯包膜尿素能明显促进春玉米对氮素吸收利用，其氮肥利用率达32.5％~40.0％，但其与商品包膜尿素(19.5％)之间无显著差异。自研制聚氨酯包膜尿素和商品包膜尿素处理下土壤无机氮素含量峰值分别出现在28和15 d前后，其在土壤中氮素释放时间分别达70和60 d以上。春玉米全生育期内(91 d)，自研制聚氨酯包膜尿素处理下土壤无机氮含量都高于商品包膜尿素和NPK处理。因此，与商品包膜尿素和NPK处理相比，自研制聚氨酯包膜尿素的氮素释放时间长且氮素供应充足。

Study on N releasing characteristics of several coated urea by polyurethane

The turnable pan coating method was used to produce three kinds of coated urea by polyurethane, taking polyure-thane as the main coating ingredient, and paraffin wax, modified kaolin, dicyandiamide ( calcium oxide) as the mixture in-gredients. A water immersion test and pot experiment was carried out to study on N releasing characteristics of three kinds of independent development of coated urea by polyurethane, respectively;and the effects of six fertilizer treatments on the growth, N uptake and utilization of spring maize under the same N, P, K nutrients input were investigated. The results indicated that there were very similar tendencies of accumulative N releasing ratio of three kinds of independent development of coated urea by polyurethane in water (25℃). The initial releasing rate in 24 h were 2. 04% ~3. 64% (≤15%), and accumulative N re-leasing ratios in 28 d were 29. 88% ~34. 80% (≤80%) , which were accorded with national standards of slow release fertiliz-ers. N uptake and utilization of spring maize in treatments independent development of coated urea by polyurethane was signifi-cantly improved compared to treatment NPK. N use efficiencies of these coated urea by polyurethane were ranged from 32. 5% ~40. 0%. there was no significant difference from commodity coated urea ( 19. 5%) . The peaks of soil mineral N content in treatments independent development of coated urea by polyurethane and commodity coated urea were happened before and after 28 and 15 d, and the corresponding N releasing periods were greater than 70 and 60 d, respectively. During the growing period of spring maize ( within 91 d) , soil mineral N content in treatments independent development of coated urea by polyurethane was always higher than those in treatments commodity coated urea and NPK. Therefore, in contrast to commodity coated urea and NPK fertilizers, N releasing days was even longer and N supplying was rather enough during the early growing period of spring maize in these independent development of coated urea by polyurethane.