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Efforts to mitigate the negative impacts of flooding on rice production have focused mainly on varietal improvement. However, there is the need to find a technological fit between genotypes and nutrient management strategies to ensure sustainable production in submergence-prone areas. During the 2016 and 2017 growing seasons, we compered effectiveness and resilience of the traditional farmer practice of rice fertilization (FP), where fertilizers are surface broadcast, with three fertilization strategies commonly used in rice production systems to determine the most efficient fertilization strategy for submergence-prone rice production areas in northern Ghana. The fertilization strategies were (i) urea deep placement technology (UDP), (ii) microdosing (MD) and (iii) modification of the farmer practice (MFP), where fertilizers are soil-incorporated. Two submergence-tolerant rice varieties, NERICA L-19 and NERICA L-49 were used as test varieties. Compared to production under non-submergence conditions, UDP resulted in <30% decrease in grain yield under submergence conditions; MFP by 57%, MD by 60% and FP by 75%. In submergence-prone areas, agronomic efficiency increased by 4.4× in UDP, relative to FP, 1.7× in MFP, and 1.5× in MD. Only UDP resulted in positive gross profit margin for rice production under submergence conditions. All other fertilization strategies resulted in negative gross profit margin values. From the combined results we conclude that under submergence-prone environment UDP is the most effective and resilient fertilization strategy for rice production and that farmers will realize profitable return on their investment with a combined use of submergence-tolerant rice cultivars and UDP fertilization strategy. [ABSTRACT FROM AUTHOR]

Risk efficiency of rice grain yield and returns to farm operators' household resources generated from an improved short-duration cover crop fallow system were compared with (traditional) natural bush fallow, and continuous rice-cropping systems. The improved fallow system involved maintainingCalopogonium mucunoides, seeded into a natural bush fallow for 2 years before planting to rice. With no chemical fertilizer application, which reflects farmers' practice in the area, average grain yield for continuous rice (1,185 kg/ha) and the cropping sequence incorporating a natural bush fallow (1,175 kg/ha) did not differ, but were higher for the improved fallow system (1,304 kg/ha). This suggests that nutrient contribution from the leguminous cover crop made up for critical crop N requirements in the improved fallow. Stochastic dominance of grain yield distributions from the improved fallow system, relative to the other two cropping systems, was more dramatic with no N fertilizer application compared to treatments with 30 kg/ha N. Average returns were highest for the improved fallow system, followed by the natural bush fallow-cropping system, and then continuous rice, under the no N fertilizer treatment regime. With 30 kg/ha N fertilizer, income risk efficiency was less clear (compared to treatments with no N fertilizer), especially between continuous rice and the improved fallow treatment, because of faster N mineralization effects on continuous rice. In contrast, the improved cover crop fallow system completely dominated the natural bush fallow treatment under both fertilizer regimes. Rice production systems that incorporated the leguminous cover crop fallow were superior to the natural bush fallow system, based on both grain yield and average farm income risk-efficiency considerations. [ABSTRACT FROM AUTHOR]

Abstract: Reducing fallow periods with sown leguminous plants (i.e., Callopogonium mucunoides) was found to be a technically feasible, low-input method of improving soil nutrient levels for rice cropping in the Guinea and Sudan savannah regions of northern Ghana. However, farmers and policy makers are particularly interested in understanding whether the new rice production technology can be substituted for the traditional rice cropping systems within a whole-farm plan context and, if so, what are the likely resource allocation and financial implications to farmers. An optimal whole-farm plan that incorporates traditional (bush fallow) cropping of rice, jointly with livestock production was generated using a linear programming model, and then used to assess the economic implications of introducing the improved fallow (i.e., incorporating Callopogonium mucunoides) rice cropping system. The alternative combinations of enterprises investigated needed to be economically viable household farm units, as well as meet household food security requirements of such resource poor farmers. Introducing the new rice production technology into a base whole-farm model (i.e., under traditional rice cropping) increased rice area by 45%, and farm income above variable costs by 34%. In addition, the representative farm raises six beef cows and 72 poultry birds. In sensitivity analyses of alternative model scenarios, farm incomes were higher and more stable for farming systems using the new rice cropping technology than with the traditional whole-farm model. More widespread adoption of the new rice-based production technology will help transform existing traditional subsistence farming systems to more profitable commercial production systems. This transformation will have implications for farm structure (in terms of consolidation of highly fragmented holdings), agricultural resource management, and property rights (such as recognition of individualized rights to cropland, livestock grazing land and agricultural water resources). [Copyright &y& Elsevier]

Abstract Nutrient deficiencies are considered major constraints to rice production in sub-Saharan Africa (SSA), but a systematic, continent-wide analysis of these constraints is lacking. The objective of this study was to assess responses of rice yields to macronutrients (N, P, and K) across major rice production systems [irrigated lowland rice (IL), rainfed lowland rice (RL), and rainfed upland rice (RU)] and diverse agro-ecological zones (semi-arid, sub-humid, humid, and highlands) in SSA. Diagnostic trials were conducted in 17 countries in 18–60 farmers' fields in each of 30 sites (totaling 1037 farmers' fields), of which 12 sites were in IL, 15 in RL and 3 in RU. All trials had an NPK treatment, and three treatments in which either nitrogen (N), phosphorus (P), or potassium (K) was omitted from the NPK treatment (minus N, P, and K plots). The trials were conducted during one or two seasons. Regression between yields in the NPK and minus N plots was used for calculating N fertilizer requirement, following the approach used for the development of a nutrient management decision support tool for rice (RiceAdvice) in SSA. Site mean yields in the NPK treatment ranged from 1.4 to 7.3 t ha−1. On average, these yields were 1.1 t ha−1 higher than farmers' yields previously observed in the same sites. N was generally the most limiting nutrient, followed by P. Rice yields without N, P, and K were 68, 84, and 89% of yields in the NPK treatment, and were positively correlated with those in the NPK treatment irrespective of production systems and agro-ecological zone (AEZ). Results from a regression model across sites indicated that achieving 3, 5, and 7 t ha−1 requires N fertilizer application at an average rate of 56, 91, and 122 kg N ha−1, respectively. However, there was significant treatment by site interaction on rice yield. Site mean yields were significantly lower without N, P, and K in 93, 60, and 50% of sites as compared to the NPK treatment. Yield response to macronutrients varied across sites and was not related to production system, nor AEZ. Results from this study will help further improvement of RiceAdvice for providing decision support tailored to the particular site, zone, or production system, thereby closing yield gaps, improving fertilizer nutrient efficiency and preventing negative environmental consequences of fertilizer use. Highlights • Nutrient omission trials for rice were conducted in 1037 farmers' fields across 30 sites in 17 SSA countries. • 12, 15, and 3 sites were located in irrigated lowland, rainfed lowland, and rainfed upland, respectively. • Site mean yields in the NPK treatment ranged from 1.4 to 7.3 t ha−1. • Mean rice yields without N, P, and K were 68, 84, and 89% of yields in the NPK treatment, respectively. • N fertilizer requirements were calculated for improving nutrient management practices. [ABSTRACT FROM AUTHOR]

River floodplains are potential land resources to extend rice cultivation areas, most of which are not currently used for farming in West Africa. The major constraints that limit expansion of crop production in floodplain areas include difficulties of water management and lack of access to tractor services for land preparation at the appropriate timing for planting. However, there have been no field experiments to demonstrate the potential of rice cultivation in the floodplain ecosystems in West Africa. The objective of this study was to determine rice productivity and the responses to various fertilizer applications on different topographical positions within floodplain ecosystems. Three years of field experiments were conducted in no-till and no-bund conditions in various topographical positions including flood-prone areas with no farming history near back-swamps and conventional farmlands in the middle to upper slopes along a transect away from the White Volta River. The effects of different combinations of S, P and K fertilizer were evaluated with a constant rate of 60 kg N ha −1 applied as urea or ammonium sulfate. Rainfall varied widely, with heavy rainfall during the initial growth stage in 2012, a long dry spell during the middle stage in 2013, and consistent rainfall in 2014. Both grain yields and responses to N application tended to increase at lower elevations and near the river, benefiting from the carbon- and clay-rich soils and moisture availability, except when a submergence stress suppressed grain yield in the lowest field in 2012. The yield response was amplified with S application. On average, application of S resulted in an increase of agronomic N use efficiency from 13.4 to 22.8 kg grain per kg N applied. The effect of N and S applications were particularly large in the unutilized lowlands that produced the highest average yields ranging from 3.21 to 4.00 t ha −1 , compared to yields ranging between 0.38 and 1.40 t ha −1 achieved on conventional farmlands. Our results clearly showed empirical evidence of high productivity and high N use efficiency for rice particularly with S application in the currently unutilized floodplain areas under no-till and no-bund rainfed conditions. Although the risk of reduced yields due to complete submergence exists, cultivation of rice in productive floodplain areas offers good opportunities to increase rice production in West Africa. [ABSTRACT FROM AUTHOR]

West Africa has large areas of river floodplains, most of which are not currently used for farmland. Rice ( Oryza spp.) is a promising crop for farming in floodplains because of its high adaptability to a wide range of water environments. On the other hand, there is great variation in soil fertility and water availability even in a small area within a floodplain. Hence, we evaluated 27 rice genotypes in four fields in three years in a floodplain of the Northern Region of Ghana to investigate genotype × environment (G × E) interactions for rice yield and to identify stable, high-yielding genotypes. The genotypes consisted of O. sativa , O. glaberrima and New Rice for Africa (NERICA), and many were selected for their reported submergence resistance because of the anticipated submergence damage in the floodplain. There were large variations in yield, which ranged from 0.14 to 5.35 t ha −1 depending on the location within a floodplain, genotype and year, and there were significant genotype, environment and G × E interaction effects on yield, accounting for 24.8%, 20.2%, and 28.2%, respectively, of the total variation. The results suggested that selection of suitable location with high soil fertility and low risk of submergence is necessary to achieve high yield in a floodplain. In addition, early sowing would be effective high-yielding crop management, which reduced the risk of submergence-induced damage just after sowing and secured sufficient growth duration to achieve high yield. Genotype IR42 showed the highest average yield among environments, but its yield stability was low. On the other hand, several genotypes including Amankwatia, a local aromatic cultivar adapted to irrigated and lowland environments, and IRBL9-W[RL], a blast-tolerant variety containing the Sub1 gene for submergence tolerance, showed high, stable yield. To put these results to practical use in other floodplain areas in West Africa, physiological mechanisms causing G × E interaction for rice yield should be further studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] Inland valleys are common landscapes in Africa with an estimated area of 190Mha. [•] Inland valleys can significantly contribute to food security in sub-Saharan Africa. [•] 9.1% Of the total inland valley area could produce the current African rice demand. [•] The remaining 90.9% inland valley area could fulfil other ecosystem functions. [•] Seizing this regional inland valley potential requires a localized approach. [ABSTRACT FROM AUTHOR]

• Drainage at flowering (DF) reduced dry (DS) but not wet season (WS) rice yield. • DF had small impact on inner-canopy temp (T c) at flowering time and grain sterility. • DF greatly increased T c from late afternoon to midnight in DS but not in WS. • Negative effect of DF is ascribed to late-afternoon-to-midnight T c increase in DS. Increasing temperatures and water scarcity are concomitant threats to sustainable rice production in future climates. Although both aspects have been widely studied, little is understood about how water-saving management might affect heat-induced stress and grain yield of rice under open-field conditions. The objective was to clarify how water management practices affect daily inner-canopy temperature (T c) dynamics, flowering time, heat-induced spikelet sterility, and rice grain yield. Field experiments were conducted in four consecutive wet and dry seasons in northern Ghana. Two rice varieties, IR64 and Jasmine85, were grown under two water regimes: 1) continuous flooding (FL), and 2) continuous flooding except for an approximately 20-day drainage treatment at the flowering period (DF). Although the DF treatment was non-flooded, a high moisture content was maintained (>60 % of saturated volumetric water) to avoid any significant drought stress. The effect of water regimes on grain yield and T c differed significantly between the dry season (DS) and wet season (WS). DF significantly reduced yields by 13–26 % in the DS but not in the WS. However, the effect of DF on T c at flowering time (0.2–0.3 °C increase) and spikelet sterility (3–5% increase) was relatively small even in the DS. In contrast, DF greatly increased T c from solar noon to midnight, in particular during the period of ±3 h from sunset in the DS. At this time of the day, DF had a higher T c than FL by 0.7–0.9 °C on average. The T c did not differ between DF and FL either at flowering time or nighttime in the WS. The T c changes over the course of the day imply that water-saving management may have a higher risk of yield reduction in the DS of the sub-humid tropics not only by increasing heat-induced sterility but also by increasing late-afternoon-to-nighttime temperatures, which can cause physiological stress and respiration loss. These results can help improve water-saving management practices under contrasting climatic conditions in the sub-humid tropics and predict the combined effect of increasing temperatures and water scarcity on rice production. [ABSTRACT FROM AUTHOR]