Nitrogen (N) is the most important yield-limiting plant nutrient. Despite various measures available for improvement of N management, nitrogen use efficiency (NUE) is still very low in rice (Oryza sativa L.), particularly under rainfed conditions. A field experiment was conducted at the Regional Agricultural Research Station, Banke, Nepal, during the rainy seasons of 2017 and 2018 to study the effects of nitrogen application method on NUE and grain yields across different varieties. The field experiment was laid out in a split-plot design, consisting of three rice varieties—Arize 6444, Radha-4, and Sukkha Dhan-3—as the main plots and five fertilizer treatments in sub-plots, and replicated thrice. The five fertilizer treatments included control (0 kg N ha⁻¹), broadcast prilled urea at 78 kg N ha⁻¹ and 100 kg N ha⁻¹, and deep placement of prilled urea and briquetted urea at 78 kg N ha⁻¹. Both rice variety and fertilizer treatment had a significant (p < 0.05) effect on grain yield. The hybrid variety (Arize 6444) increased grain yield by 23% compared to Sukkha Dhan-3 (4.9 Mg ha⁻¹). Deep-placed briquetted urea increased grain yield by 21–23% (6.7 Mg ha⁻¹) compared to broadcast and deep-placed prilled urea. A higher grain yield for briquetted urea positively correlated (r = 0.43) with the number of tillers per hill. Deep-placed briquetted urea increased NUE (apparent N recovery, agronomic NUE, partial factor productivity of N, and physiological efficiency by 44%, 40%, 34%, and 3%, respectively), while reducing ammonia volatilization by 57% compared to the current recommended rate of broadcast prilled urea. Our results confirm that deep placement of briquetted urea significantly increases grain yields and NUE of rainfed rice.

中文翻译：

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尼泊尔旱作条件下通过肥料施用方法提高水稻的氮素利用效率

氮是最重要的限制产量的植物营养素。尽管有各种措施可以改善氮素管理，但水稻（水稻）的氮利用效率（NUE）仍然很低，特别是在雨养条件下。在2017年和2018年的雨季期间，在尼泊尔班克地区农业研究站进行了田间试验，研究了施氮方法对不同品种的NUE和谷物产量的影响。田间试验采用分块设计进行设计，包括三个水稻品种-Arize 6444，Radha-4和Sukkha Dhan-3-作为主要地块，并在子地块中进行五种肥料处理，并重复三次。五种肥料处理包括对照（0 kg N ha^-1），以78 kg N ha ^-1和100 kg N ha ^-1撒播造粒的尿素，并以78 kg N ha ^-1深度放置造粒的尿素和团状尿素。水稻品种和肥料处理对谷物产量都有显着影响（p <0.05）。与Sukkha Dhan-3（4.9 Mg ha ^-1）相比，杂种（Arize 6444）的谷物产量提高了23％。深层压块尿素可将谷物产量提高21–23％（6.7 Mg ha ^-1）与撒播的深层尿素相比。压块尿素的较高谷物产量与每座小山的分ers数量呈正相关（r = 0.43）。深度放置的压块尿素可增加NUE（表观N回收率，农艺性NUE，N的部分因子生产力和生理效率分别提高44％，40％，34％和3％），而与之相比，氨气挥发减少57％当前建议的播撒造粒尿素比率。我们的结果证实，深层压成块状尿素可显着提高雨养水稻的谷物产量和NUE。