Rice is a staple food and cash crop for smallholder farmers in sub-Saharan Africa; however, yields are very low, with indications that both macro and micro-nutrients may limit rice productivity in East Africa next to the need for good agronomic practices. Diagnostic on-farm experiments were conducted in Uganda and Tanzania between 2015 and 2017 to assess the contribution of macro, secondary and micro-nutrients on lowland rice yield and identify options by which smallholder farmers can increase productivity. All treatments included good agronomic practices combined with: zero fertilisation as a control, NPK fertilisation with and without secondary and micro-nutrients (B, Mn, Zn, Cu, Mg, S), and/or treatments where B, Mn and Zn were omitted one at a time from the NPK + secondary and micro-nutrient treatment.

NPK fertilisation significantly (p < 0.05) increased grain yield under irrigated condition by ca. 32 and 29 % during 2015 and 2016, and 24 and 100 % during 2016 and 2017 in Tanzania and Uganda, respectively; however, inconsistent effects were observed under rainfed condition. Observed higher yields corresponded mainly to higher panicle number with an additive effect of grains per panicle indicating major effects were at earlier growth stages supporting higher sink size development. Adding secondary and micro-nutrients to NPK enhanced yield significantly (p < 0.05) under irrigated condition in Tanzania 2015 and 2016 by 7 and 11 %, respectively, while varying results were obtained under rainfed condition. In Uganda, no significant (p> 0.22) effects of secondary and micro-nutrients were observed in both years and growing conditions.

This study indicates that the first step to improving lowland rice productivity is proper water management, under otherwise also good crop management in terms of timely transplanting and weeding, and further yield gains can be realised with NPK fertilisation. Secondary and micro-nutrients were effective only when NPK were applied and on the fluvisols of Tanzania, and were not co-limiting yield on the plintosols of Uganda.

水稻是撒哈拉以南非洲小农的主食和经济作物；然而，产量非常低，有迹象表明，除了需要良好的农艺实践之外，宏量和微量营养素都可能限制东非水稻的生产力。2015 年至 2017 年在乌干达和坦桑尼亚进行了诊断性农场试验，以评估宏观、次要和微量营养素对低地水稻产量的贡献，并确定小农提高生产力的选项。所有处理都包括良好的农艺实践，并结合：零施肥作为对照，有和没有次要和微量营养素（B、Mn、Zn、Cu、Mg、S）的 NPK 施肥，和/或 B、Mn 和 Zn 为从 NPK + 二次和微量营养素处理中一次省略一个。

NPK 施肥显着 (p < 0.05) 增加了灌溉条件下的谷物产量约 2015 年和 2016 年分别为 32% 和 29%，坦桑尼亚和乌干达 2016 年和 2017 年分别为 24% 和 100%；然而，在雨养条件下观察到了不一致的影响。观察到的较高产量主要与较高的穗数相对应，每穗粒数具有累加效应，表明主要效应发生在早期生长阶段，支持较高的水槽尺寸发展。在坦桑尼亚 2015 年和 2016 年灌溉条件下，向 NPK 中添加次生和微量营养素分别显着提高了产量（p < 0.05）7 和 11%，而在雨养条件下获得了不同的结果。在乌干达，在年份和生长条件下均未观察到次要营养素和微量营养素的显着 (p> 0.22) 影响。

这项研究表明，提高低地水稻生产力的第一步是适当的水管理，否则在及时移栽和除草方面也有良好的作物管理，并且通过 NPK 施肥可以进一步提高产量。次要营养素和微量营养素仅在施用 NPK 时对坦桑尼亚的河流土壤有效，并且不会共同限制乌干达的植物土壤的产量。