Dry direct-seeded rice (DDSR) is an adaptive practice used in rainfed lowlands of tropical Asia where insufficient rainfall at the onset of the wet season makes it difficult to successfully transplant rice seedlings. However, basic guidelines for nutrient management to support DDSR are lacking. Here, we evaluated crop growth and yield in DDSR with different N fertilizers (ammonium sulfate, urea, and coated compound fertilizer) applied at different timings. The total N rate was fixed at 100 kg ha⁻¹. On-station trials were conducted at the International Rice Research Institute, in the Philippines, during the wet seasons of 2017 and 2018, and 17 on-farm trials were conducted in nine provinces in 2018 and 2019. In the on-station trials, ammonium sulfate did not increase yield compared with urea and coated compound fertilizer in either year. Application of N fertilizers at sowing promoted plant N uptake and early shoot growth, but the effect of the timing of N application on yield was not significant. The on-farm trials showed that a uniform N management recommendation is unlikely to be effective in DDSR. Yield increased significantly with coated compound fertilizer relative to the uncoated fertilizers in clay and silty clay soils, but not in other soil types. In general, flexible timing of the first application of N, ranging from 0 to 30 days after sowing, had no significant effect on yield, but the omission of N application at sowing reduced yield by 13–25% in two trials on sandy soils with a low nutrient-holding capacity.

干直播稻 (DDSR) 是一种适应性做法，用于热带亚洲雨养低地，雨季开始时降雨不足，难以成功移植水稻幼苗。然而，缺乏支持 DDSR 的营养管理基本指南。在这里，我们评估了 DDSR 在不同时间施用不同氮肥（硫酸铵、尿素和包膜复合肥）的作物生长和产量。总氮含量固定为 100 kg ha ^-1. 2017 年和 2018 年雨季在菲律宾国际水稻研究所进行了现场试验，2018 年和 2019 年在 9 个省进行了 17 次农场试验。在现场试验中，铵与尿素和包膜复合肥相比，硫酸盐在任一年份均未增产。播种时施氮肥促进植株吸氮和早期枝条生长，但施氮时机对产量的影响不显着。农场试验表明，统一的氮管理建议在 DDSR 中不太可能有效。在粘土和粉质粘土中，与未包膜肥料相比，包膜复合肥的产量显着增加，但在其他土壤类型中没有。一般来说，第一次申请N的时间灵活，