Progress in research on site-specific nutrient management for smallholder farmers in sub-Saharan Africa

Increasing fertilizer access and use is an essential component for improving crop production and food security in sub-Saharan Africa (SSA). However, given the heterogeneous nature of smallholder farms, fertilizer application needs to be tailored to specific farming conditions to increase yield, profitability, and nutrient use efficiency. The site-specific nutrient management (SSNM) approach initially developed in the 1990 s for generating field-specific fertilizer recommendations for rice in Asia, has also been introduced to rice, maize and cassava cropping systems in SSA. The SSNM approach has been shown to increase yield, profitability, and nutrient use efficiency. Yield gains of rice and maize with SSNM in SSA were on average 24% and 69% when compared to the farmer practice, respectively, or 11% and 4% when compared to local blanket fertilizer recommendations. However, there is need for more extensive field evaluation to quantify the broader benefits of the SSNM approach in diverse farming systems and environments. Especially for rice, the SSNM approach should be expanded to rainfed systems, which are dominant in SSA and further developed to take into account soil texture and soil water availability. Digital decision support tools such as RiceAdvice and Nutrient Expert can enable wider dissemination of locally relevant SSNM recommendations to reach large numbers of farmers at scale. One of the major limitations of the currently available SSNM decision support tools is the requirement of acquiring a significant amount of farm-specific information needed to formulate SSNM recommendations. The scaling potential of SSNM will be greatly enhanced by integration with other agronomic advisory platforms and seamless integration of digital soil, climate and crop information to improve predictions of SSNM recommendations with reduced need for on-farm data collection. Uncertainty should also be included in future solutions, primarily to also better account for varying prices and economic outcomes.

Assessment of Nutrient Expert ®-Hybrid maize model on productivity and profitability of winter maize in Terai region of eastern Nepal

Inadequate, unscientific, and lack of optimum utilization of fertilizer management devoid of site-specific nutrient management have been the significant constraints of maize (Zea mays L.) production in Nepal. Therefore, a multi-locational farmers' field was planned and executed at two VDCs of Morang district in the Terai region of Nepal from December 2015 to May 2016. Nutrient Expert (NE) and Farmer's Fertilizer Practices (FFP) treatments were imposed in a randomized complete block design (RCBD) with twenty replications. The research explored highly significant results in terms of plant number m⁻², cob numbers m⁻², cob length, kernel rows cob⁻¹, kernels kernel row⁻¹, test weight, grain, stover, and biological yields and harvest index. NE showed the highest yield (8.06 tons ha ^-1) among the two treatments tested than FFP (4.52 tons ha ⁻¹). While comparing net revenue, NE-based fertilizer recommendation gave the significantly higher (NRs.151.116 thousand ha ⁻¹ equivalent to $1281 ha ⁻¹) result than FFP (NRs.84.834 thousand ha⁻¹ equivalents to $707). The result suggests adopting NE practices to minimize the yield gaps and increase the productivity of maize in Morang and adjoining agro-climatic conditions of eastern Terai, Nepal.

Co-benefits of nutrient management tailored to smallholder agriculture

Plant nutrition plays a central role in the global challenges to produce sufficient and nutritious food, lessen rural poverty, and reducing the environmental footprint of farming. Site-specific nutrient management (SSNM) provides field-specific solutions for smallholder farmers, potentially creating co-benefits of increased productivity and sustainability. Here we perform the first meta-analysis comparing SSNM with farmers’ fertilizer practice for maize, rice and wheat using 61 published papers across 11 countries. Relative to the farmer practice, across all crops SSNM increased grain yield by 12% and profitability by 15% with 10% less fertilizer nitrogen applied, thereby improving nitrogen use efficiency and reducing nitrogen pollution to the environment. Delivering it to millions of smallholder farmers requires use of digital decision support tools, but also policy incentives, links with financial and input supply services, and enhancing public-private partnerships.

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Meta-analysis was performed to compare SSNM with farmers' fertilizer practice (FFP).

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Data are from 61 published papers across 11 countries on maize, rice and wheat.

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Overall, 0.6 Mg ha⁻¹ yield and US$ 140 ha⁻¹ profit gains were obtained with SSNM.

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These benefits were achieved using 10% less N fertilizer than FFP.

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Agronomic N use efficiency was 40% greater with SSNM than FFP.

Field-specific nutrient management using Rice Crop Manager decision support tool in Odisha, India

The requirement of rice (Oryza sativa L.) for fertilizer can depend on crop and soil management practices, which can vary among fields within a rice-growing area. A web-based decision support tool named Rice Crop Manager (RCM) was developed previously to calculate field-specific rates of fertilizer N, P, and K for rice in Odisha State in eastern India. We compared field-specific nutrient management calculated by RCM with farmers' fertilizer practice (FFP) and a blanket fertilizer recommendation (BFR), which used a uniform 80 kg N ha-1, 17 kg P ha-1, and 33 kg K ha-1. A total of 209 field trials were conducted in two seasons (kharif and rabi) for two years across ten districts in six agro-climatic zones. Grain yield was consistently higher with fertilization recommended by RCM than with FFP. Higher yield with RCM was attributed to a combination of applying more of the total fertilizer N at the critical growth stage of panicle initiation, applying more fertilizer N in kharif, and applying zinc. The RCM recommendation frequently increased yield compared to BFR as a result of improved N management, which included the adjustment of N rate for a target yield set slightly higher than historical yield reported by a farmer. Fertilization based on RCM rather than BFR reduced the risk of financial loss. The effectiveness of an RCM recommendation relative to BFR and FFP was consistent across rice varieties with different growth duration, irrigated and rainfed rice, and three categories of soil clay content. The RCM recommendation failed to increase yield relative to BFR in one of the six agro-climatic zones, where a higher rate of fertilizer P and/or K was apparently required. The nutrient management calculations used by RCM can be improved as new information and research findings become available. Experiences with RCM in Odisha can help guide the development of comparable nutrient management decision tools in other rice-growing areas.