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Increasing productivity per unit area, hence closing the yield gap, is key to meeting cereal demand in sub-Saharan Africa. We assessed, with 114 farmers, the contribution of recommended agronomic practices (RAP) with or without NPK fertilization on yield gaps, and options to intensify productivity. Treatments included farmers’ practice (FP) as control, RAP with and without NPK, and farmer-selected best practices geared towards intensification (farmers’ intensification practice, FIP). RAP without fertilization and FIP significantly increased grain yield, each by ca. 12%, whereas RAP+NPK application produced ca. 33% extra yield, over FP. RAP gave the highest mean net income (ca. USD 220 ha−1), fertilizer costs made RAP+NPK gave the lowest mean net income (ca. USD 50 ha−1). Weeding and fertilization timing contributed most to yield variation among fields. Delay in weeding and fertilization created an average yield loss of 5.3 and 1.9 g m−2, per day delay, respectively. Exploitable yield gap averaged 24 and 29%, respectively, across treatments and under FP. RAP, FIP, and RAP+NPK reduced the exploitable yield gap to 25, 26, and 12%, respectively. We conclude that different yield gap levels can be exploited by smallholder farmers in lowland rice systems as RAP, FIP, and RAP+NPK allow yield gap reduction, although fertilization poses a risk to profit at current rice and fertilizer prices. To realize yield gains, farmers with good water management should combine timely weeding with other crop management practices.

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 t

Fertilizer nutrients are essential for food and nutrition security, but a large proportion of nutrients applied to soil are lost because they are unavailable to plants. The extent of these nutrient losses exceeds safe and sustainable limits. Societal awareness of this is limited because it can take many seasons for nutrient-loss impacts to become visible. We propose that Innovative Fertilizers and Application Technologies (IFAT) could help reduce nutrient losses and thus reduce pressure on resources, and provide important micronutrients for human health. However, transformation of the fertilizer sector through stakeholder engagement, policy interventions, and public–private initiatives will be required to unlock the full potential of IFAT. Summary. Strategies for delivering sustainable food systems require significant reduction in yield gaps and food system inefficiencies. Mineral fertilizers will play a critical role in achieving both of these aims. However, reduction in nutrient losses from mineral fertilizer use to levels that are considered sustainable has not been achieved and has been estimated to be unachievable, even with optimized practices for current products. We argue that Innovative Fertilizers and Application Technologies (IFAT) are needed to address the daunting and interlinked food, agricultural, and environmental challenges facing humanity and the planet. We define IFAT as a set of fertilizer products and technologies that are designed by taking the physiological needs of plants (such as nutrient uptake, redistribution, and utilization) as the entry point in the fertilizer development process, rather than starting first with chemistry. This approach aims for the timely and targeted delivery of nutrients in balanced quantities. We propose that this can result in multiple food, agricultural, and environmental benefits, including increased yield, improvements in nutritional quality, enhanced crop resilience, and reduced emission of greenhouse gases (GH