Challenges and opportunities for improving N use efficiency for rice production in sub-Saharan Africa

Abstract

In sub-Saharan Africa (SSA), rice production from smallholder farms is challenged because of a lack of fertilizer inputs and nutrient-poor soils. Therefore, improving nutrient efficiency is particularly important for increasing both fertilizer use and rice yield. This review discusses how to improve the return from fertilizer input in terms of agronomic N use efficiency (AE N), that is, the increase in grain yield per kg of applied N, for rice production in SSA. The AE N values we summarized here revealed large spatial variations even within small areas and a certain gap between researcher-led trials and smallholder-managed farms. Experimental results suggest AE N can be improved by addressing spatial variations in soil-related factors such as P, S, Zn, and Si deficiencies and Fe toxicity in both irrigated and rainfed production systems. In rainfed production systems, differences in small-scale topography are also important which affects AE N through dynamic changes in hydrology and variations in the contents of soil organic carbon and clay. Although empirical evidence is further needed regarding the relationship between soil properties and responses to fertilizer inputs, recent agricultural advances have generated opportunities for integrating these micro-topographical and soil-related variables into field-specific fertilizer management. These opportunities include UAV (unmanned aerial vehicle) technology to capture microtopography at low cost, database on soil nutrient characteristics at high resolution and more numbers of fertilizer blending facilities across SSA, and interactive decision support tools by use of smartphones on site. Small-dose nursery fertilization can be also alternative approach for improving AE N in adverse field conditions in SSA.

Optimizing the Phosphorus Concentration and Duration of Seedling Dipping in Soil Slurry for Accelerating the Initial Growth of Transplanted Rice

“…However, world resources of P are finite and thus, P should be used as efficiently as possible in order to conserve the base resources [4]. Efficient P fertilizer management is also key to improving rice yield for smallholder farmers who use few external inputs, such as in the case of Sub-Saharan Africa [5]. Therefore, it is necessary to find appropriate strategies for the effective use of P fertilizers in rice production systems.…”

Pronounced effect of farmyard manure application on P availability to rice for paddy soils with low total C and low pH in the central highlands of Madagascar

“…However, rice yields in SSA have remained low because of several biotic and abiotic stresses. Among these various stresses, P deficiency is a major constraint for rice production in highly weathered soils in SSA (Dogbe et al, 2015;Saito et al, 2019). P deficiency to rice is commonly observed in Madagascar, the second largest rice producer in SSA, which is due to high levels of P-fixing iron (Fe) or aluminum (Al) oxyhydroxides in soils (Nishigaki et al, 2019) and little P fertilizer inputs (Rabeharisoa et al, 2012;Tsujimoto et al, 2019).…”

“…Among these various stresses, P deficiency is a major constraint for rice production in highly weathered soils in SSA (Dogbe et al, 2015;Saito et al, 2019). P deficiency to rice is commonly observed in Madagascar, the second largest rice producer in SSA, which is due to high levels of P-fixing iron (Fe) or aluminum (Al) oxyhydroxides in soils (Nishigaki et al, 2019) and little P fertilizer inputs (Rabeharisoa et al, 2012;Tsujimoto et al, 2019). Our previous on-farm experiments demonstrated that the yield gap between P-fertilized and non-P-fertilized treatments could reach up to 2.5 t ha -1 in the central highlands of Madagascar (Andriamananjara et al, 2016).…”

“…The FYM can be defined as a mixture of organic materials such as animal droppings, crop residues, and fodder which are piled nearby the homesteads. A recent survey showed that 16.3% of agricultural households use organic fertilizer, mainly FYM, whereas only 0.5% use mineral fertilizer in the central highlands of Madagascar (Tsujimoto et al, 2019).…”

Improved Upland Rice: Adaptability, Agronomic and Farmer Acceptability Assessment under Semi-Arid Conditions of South Western Uganda

“…Most of the local paddy rice varieties grown in wetlands are late maturing (120 -140 days), and susceptible to diseases, indicating a need to adopt and adapt the improved varieties to the prevailing farming conditions. Moreover, decline in soil fertility has also caused an increase in the cost of production [7], and overuse of fertilizers that may eventually have a negative impact on the entire wetland ecosystem. Therefore, enhancing the ability of rice plants to tolerate biotic and abiotic stresses is the current strategy for increasing agricultural productivity worldwide.…”