Abstract: In order to explore the effect of reduction application of controlled-release urea on the yield of early-rice and its reduction potential in Southern China under the condition of one-time fertilization, a plot experiment was conducted in Dongting Lake, Hunan Province, for two consecutive years from 2018 to 2019. Four treatments including no nitrogen fertilizer (CK), conventional fertilization (CU), polyurethane coated urea (PuCU) and 80% polyurethane coated urea nitrogen (0.8PuCU) were set up  to study the effect of reduction application of polyurethane coated urea on the yield, yield components, growth and economic benefit of early-rice. The results showed that different application treatments of controlled-release urea had significant (P<0.05) or extremely significant (P<0.01) effects on the yield, yield components and economic benefits of double-cropping early-rice. Compared with CU treatment, the yield and economic benefit of double-cropping early-rice in PuCU treatment  increased by 11.99% and 12.99%, respectively, and the effective panicle number, total spikelet number and total grain number  increased by 5.73%, 11.67% and 16.22%, respectively; the yield and economic benefit in 0.8PuCU treatment  increased by 2.68% and 4.96%, respectively, and the effective panicle number, total spikelet number and total grain number  decreased by 0.13%, 1.97% and 0.32%, respectively. It could be found that PuCU treatment was the best among the four treatments. Although 0.8 PuCU treatment reduced the amount of fertilizer applied, it still had the potential for increasing yield and improving efficiency compared with CU treatment, and its ratio of output to input was the highest. Correlation analysis showed that plant height, spike length, effective panicle number, total spikelet number and total grain number were significantly correlated with grain yield (P<0.05). To sum up, the application of polyurethane coated urea could effectively improve the yield composition of double-cropping early rice in Dongting Lake region, and reducing the application rate by 20% could not only stabilize the yield but also reduce the extravagant absorption of nitrogen, which was a more suitable fertilization method. However, there were differences in the controlled release effect of different coated fertilizers and the yield components of different crops, it was necessary to select the appropriate coated fertilizers according to the demand of crop varieties in local production.

Key words: double-cropping early rice, polyurethane coated urea, reduction application, yield, economic benefit

摘要： 为探究一次性施肥条件下包膜尿素减量施用对南方双季早稻产量的影响及减施潜力，于2018—2019年连续两年在湖南省洞庭湖典型双季稻种植区开展小区试验，设置不施氮肥（CK）、常规施肥（CU）、聚氨酯包膜尿素（PuCU）和聚氨酯包膜尿素氮量减20%（0.8PuCU）共4个处理，研究聚氨酯包膜尿素减施对双季早稻生长、产量、产量构成因素及经济效益的影响。结果表明，包膜肥料不同用量处理对双季早稻产量、产量构成因素及经济效益均存在显著（P<0.05）或极显著影响（P<0.01）。与CU处理相比，PuCU处理的双季早稻两年产量和经济效益分别平均提高11.99%和12.99%，有效穗数、总颖花数和总实粒数分别平均提高5.73%、11.67%和16.22%；0.8PuCU处理的双季早稻两年产量和经济效益分别平均提高2.68%和4.96%，有效穗数、总颖花数和总实粒数分别平均降低0.13%、1.97%和0.32%。可见，4个处理中以PuCU处理效果较好；而0.8 PuCU处理虽减少了肥料施用量，仍具有增产增效潜力，且产投比最高。相关分析表明，株高、穗长、有效穗数、总颖花数和总实粒数与籽粒产量的相关性均达显著水平（P<0.05）。综上，施入聚氨酯包膜尿素可有效改善洞庭湖区域双季早稻产量构成，进一步减施20%能在稳产的同时减少氮素奢侈吸收，收益率更高，是一种较为合适的施肥方法。然而不同包膜肥的控释效果及不同作物产量构成存在差异，实际生产中应根据作物品种需求进行选择。

关键词: 双季早稻, 聚氨酯包膜尿素, 减施, 产量, 经济效益