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Climate change and variability challenge crop productivity and resource use efficiency in West Africa. Despite abundant research on climate change impact on crop yields and food security, little is known about climate change effects on the resource use efficiencies of the main staple crops in the dry savanna agro-ecological zone of northern Benin, West Africa. This study assessed the impact of climate change on water- and N-use efficiencies, and yields of maize and sorghum in the dry savanna of northern Benin considering three soil fertility management options (return of crop residues, mineral NPK fertilizer application, and combinations of both) and three bias-corrected ensemble mean predictions (BNU-ESM, CanESM2, and MPI-ESM-MR models) of future climate (2080–2099) under Representative Concentration Pathways (RCPs) of 2.6, 4.5, and 8.5. Seasonal rainfall is projected to decrease by 2% under RCP 2.6 and by 4% under RCP 4.5, and to increase by 1% under RCP 8.5 relative to the baseline mean (1986–2005). Increasing trends in minimum temperature of +1.0 °C (RCP 2.6), +2.0 °C (RCP 4.5), +4.7 °C (RCP 8.5) and maximum temperature of +1.1 °C (RCP 2.6), +2.0 °C (RCP 4.5), +4.6 °C (RCP 8.5) are also predicted. Solar radiation was projected to decrease by about 0.4 MJ m−2 d-1. Under these projected climate scenarios, both CERES-Maize and CERES-Sorghum simulated positive responses in aboveground biomass accumulation during the vegetative growth stages. The predicted increase in aboveground biomass growth will be largest under RCP8.5 and smallest under RCP 2.6. This impact can be enhanced by improved soil fertility management, albeit with a crop-specific magnitude. Across the soil fertility management options, CERES-Maize predicted decreases in water-use efficiency by 17–53%, partial factor productivity of nitrogen (N) by 10–47%, and internal N-use efficiency by 5–33% for maize. Similarly, CERES-Sorghum simulated decreases in water-use efficiency (23–51%), partial factor productivity of N (22–49%), and internal N-use efficiency (13–47%) for sorghum. The largest overall loss in resource efficiency and yield were predicted for the RCP 8.5 scenario. The projected climate change for the dry savanna in northern Benin will likely reduce water- and N-use efficiencies as well as grain yields of maize and sorghum considerably but these results should be treated with caution due to shortcomings in the models structure for dealing with effects of enhanced CO2. For reliable assessments of climate change impact on WUE, it is critically important to update parameterization and code of the CERES crop models in DSSAT to have a sufficiently strong effect of CO2 on stomatal conductance and on transpiration.

New technologies combined with improved genetics and farmer access are important components required to improve productivity and efficiencies of cropping systems. The ability of the public and private sector to provide these components to farmers often vary considerably and can be challenging because of limited resource allocation and investment in institutions designed to provide these services. Partnerships among national programs where resources are limited and external entities can provide an effective platform to deliver improved cultivars and production and pest management practices that increase crop yield and economic viability of resource-poor farmers. In this note, we describe a partnership between the Council for Scientific and Industrial Research-Crops Research Institute (CSIR-CRI) in Ghana, the International Center for Research in the Semi-Arid Tropics (ICRISAT), the US Agency for International Development Peanut Collaborative Research Support Program (USAID Peanut CRSP), the Feed the Future Innovation Lab on Peanut Productivity and Mycotoxin Control (PMIL), and North Carolina State University (NCSU) that resulted in the release of two ICRISAT-derived lines as cultivars to farmers in Ghana. The cultivars Otuhia (Arachis hypogaea L.) and Yenyawoso (Arachis hypogaea L.) were released by CSIR-CRI in 2012 following evaluations of breeding lines beginning in 1999. This case study provides insight into the research focus and timeline that occurred with this partnership during the research and development process. A portion of the data obtained to support release of these cultivars is provided.

Agriculture is a critical element of the West African Sudan Savanna’s economy and the main livelihood strategy for many people, where food insecurity and poverty are widespread. Low soil fertility, high intra and inter-annual rainfall variability together with limited ability to invest in new technologies are among the major constraints to the predominantly smallholder, rainfed crop production in the region’s mixed crop-livestock systems. We evaluated the effect of tillage practices (contour and reduced tillage), nitrogen fertilizer rates (no nitrogen -N0, recommended nitrogen -NREC and high nitrogen-N2REC) and residue management (improved and standard) on the yield of maize, cotton and sorghum for two landscape positions (upslope and footslope) for four growing seasons in three locations in the Sudan Savanna region of Burkina-Faso (Dano), Ghana (Vea) and Republic of Benin (Dassari). The studies aimed at assessing the potential of residue retention, tillage practices and nitrogen fertilization to (1) increase average yields and (2) stabilize yields under sub-humid conditions. Over the 4 year study period, across the 3 locations recommended N produced 17% higher crop yields than the N0 treatment. It was not worthwhile to double the recommended N as there was no yield benefit of applying more fertilizer. The results revealed no consistent interactions across sites except crop type and nitrogen fertilization. Stability analysis revealed that contour ridging was superior in stabilizing yield. Evaluation of the relative maize yield stability on different levels of nitrogen depicts variation and there is a tendency for an inverse relationship between mean yield of nitrogen levels and its relative yield stability since nitrogen application did not increase yield stability. The outcome of cost benefit analysis revealed that, return per cash invested favored non-degraded sites with cotton production and in years with favorable rainfall conditions. Thus, in the Sudan savanna of West Africa, it is economically risky to invest in mineral N fertilizers when cropping on degraded soils or when rainfall is expected to be erratic.

Cotton is an important cash crop in many West African countries. Hence, its sustainable production will support the national economies as well as the livelihoods of the farming population alike and in turn help easing wide-spread poverty. However, future climate change may affect the productivity of cotton in West Africa. Therefore, the objectives of this study were to (i) parameterize the Cropping System Model- CROPGRO-Cotton to simulate growth, seed cotton yield, and in-season soil water dynamics and nitrogen (N) uptake, and (ii) apply the model to estimate potential climate change impacts on cotton growth, yields, and water- and N- productivity under different soil-fertility management practices. The CROPGRO-Cotton model was first parameterized and evaluated using datasets collected in three field experiments conducted in 2014 and 2015 in the Dry Savanna of northern Benin, West Africa. The model was next applied to determine long-term responses of cotton to historical (1986–2015) and projected climate (2080–2099) for three Representative Concentration Pathways (RCPs 2.6, 4.5, and 8.5). CROPGRO-Cotton accurately simulated in-season soil water dynamics (nRMSE of 12–27%, d-values of 0.79–0.88), N uptake (nRMSE of 31–44%, d-values of 0.89–0.96), and biomass accrual (nRMSE of 31–46% and d-values of 0.91–0.97), as well as seed cotton yield at harvest (nRMSE of 24–39% and d-value of about 0.81). The model predicted higher seed cotton yield with planting dates in June compared to July. Under the climate change scenario of RCP2.6, CROPGRO-Cotton predicted a decrease in water use efficiency (WUE) by 20% without any soil amendment, and by 4% with an integrated soil-crop management compared to the historical run, but an increase of 2% with a high use of mineral fertilizer. With the RCP4.5 and 8.5 scenarios, the predicted changes in WUE varied between −1% and 17% across the soil fertility management options. CROPGRO-Cotton predicted increases in N-partial factor productivity by 7 to 31%. The N uptake varied between −7% and 46% whilst seed cotton yield varied between −7 and 41%. The findings underlined that the predicted future increases in water and N productivity in cotton will be driven by CO2 fertilization, increases in temperatures as well as rainfall variability, but at the expense of soil fertility leading to soil mining. Yet, even if cotton, unlike some other crops in the region, will likely respond positively to climate change, adequate soil fertility management practices are essential to ensure efficient and sustainable water- and N- use in the expected future.

Sustainable production practices are needed to enhance water and nutrient use efficiencies in the cropping systems of West Africa, especially in face of predicted climate change for the region. Crop simulation models may assist in exploring alternative management systems for optimizing water and nutrient use efficiencies, increasing crop production, and easing food insecurity. The twofold objectives were: (i) to access the ability of the CERES-Maize and CERES-Sorghum models for predicting yields, nitrogen (N) and phosphorus (P) uptake, and in-season soil water and N dynamics during maize and sorghum growth; (ii) to use the models to assess the effects of different nutrient management strategies on soil C and N, and crop water and N use efficiencies considering 30 years of historical weather variability in the dry savanna agro-ecological zone of northern Benin, West Africa. Both models were calibrated with data from a researcher-managed field trial (2014) and validated with independent findings (2015). The models were next evaluated with datasets collected from researcher- and farmer-managed field trials conducted under rainfed and supplementary irrigation conditions (2014–2015). The parameterized CERES-Maize and CERES-Sorghum models accurately predicted biomass accumulation with a normalized root mean square error (nRMSE) of 18% and 17%, respectively, and an index of agreement (d) of 0.98 for both crops in non-nutrient- and non-water-stressed conditions. Under rainfed and rainfed with supplementary irrigation conditions, both with and without mineral fertilizer application, CERES-Maize predicted biomass accumulation with nRMSE (d) of 10–22% (0.96–0.99), while CERES-Sorghum reached accuracies of 13–29% (0.97–0.99). Grain yield was simulated with nRMSE (d) of 19% (0.93) and 15% (0.89) by CERES-Maize, and 16% (0.91) and 15% (0.80) by CERES-Sorghum in researcher-managed and farmer-managed fields, respectively. CERES-Maize predicted reasonably well nutrient uptake with nRMSE (d) ranging from 14 to 40% (0.89–98) for N and between 24 and 49% (0.90–0.98) for P. Similarly, CERES-Sorghum simulated N uptake with nRMSE of 17–49% and d-values of 0.87–0.98, and P uptake with nRMSE of 42–62% and d-values of 0.82–0.93. Values of nRMSE (d) between predicted and measured in-season soil water and N dynamics were 6–13% (0.61–0.87) and 46–58% (0.61–0.76) with CERES-Maize, and 14–20% (0.75–0.89) and 35–56% (0.62–0.82) with CERES-Sorghum, respectively. The models simulated improved soil organic C and inorganic N, water and N use efficiencies, and grain yields with the integrated soil-crop management system compared to un-amended soil and high mineral fertilizer use options under 30 years of weather variability. Both models are thus appropriate tools not only to explore potential impacts of predicted climate change on soil water and nutrient use efficiencies, but also to frame more sustainable intensification measures in the maize- and sorghum-based production systems of West Africa.

Weeds and diseases can reduce peanut (Arachis hypogaea L.) yield or increase cost of production to maintain acceptable yield. While herbicides and fungicides have limited availability in many areas...

In the Sudano-Sahelian zone of West Africa, where deforestation and cropland soil degradation occur at alarming rates, the (re-)introduction of trees on degraded lands can improve and sustain farming systems and landscapes. The shoot and root morphological traits of five woody species introduced to degraded cropland were assessed with a particular focus on the survival, early establishment and growth of saplings subjected to manuring (1 kg per plant) and drip irrigation (0.5 L of water per plant per day). Functional traits of the woody above- and belowground organs of field-grown plants were monitored for the first 15 months after planting, covering two growing (rainy) seasons and one dry season. The high survival rate (>60%), combined with a very low incidence rate ( Jatropha curcas L., Leucaena leucocephala Lam. and Moringa oleifera Lam. The mortality rate of the most drought-sensitive species Parkia biglobosa Jacq. could be reduced ten-fold through supplemental irrigation during the dry season. The fast-growing L. leucocephala , M. oleifera and J. curcas had higher values for shoot-level traits than did the slow-growing Anacardium occidentale L. and P. biglobosa . Fertilization and irrigation enhanced the shoot growth of both the fast and slow growers during the dry and growing seasons. In contrast, belowground development was either increased or reduced by fertilization and irrigation during the growing and dry seasons, but the slow growers demonstrated a more plastic response to these treatments than did the fast growers. Among the studied traits, the relative growth rate of plant as a whole (i.e. shoots and roots combined) exhibited the greatest plastic response to resource availability, thus suggesting its application in screening candidate species for afforestation efforts. Overall, the five studied species were considered suitable for the afforestation of degraded croplands, while the early growth and establishment of saplings could be boosted by irrigation and a supply of manure.

To reduce the risks of climate change, governments agreed in the Paris Agreement to limit global temperature rise to less than 2.0 °C above pre-industrial levels, with the ambition to keep warming to 1.5 °C. Charting appropriate mitigation responses requires information on the costs of mitigating versus associated damages for the two levels of warming. In this assessment, a critical consideration is the impact on crop yields and yield variability in regions currently challenged by food insecurity. The current study assessed impacts of 1.5 °C versus 2.0 °C on yields of maize, pearl millet and sorghum in the West African Sudan Savanna using two crop models that were calibrated with common varieties from experiments in the region with management reflecting a range of typical sowing windows. As sustainable intensification is promoted in the region for improving food security, simulations were conducted for both current fertilizer use and for an intensification case (fertility not limiting). With current fertilizer use, results indicated 2% units higher losses for maize and sorghum with 2.0 °C compared to 1.5 °C warming, with no change in millet yields for either scenario. In the intensification case, yield losses due to climate change were larger than with current fertilizer levels. However, despite the larger losses, yields were always two to three times higher with intensification, irrespective of the warming scenario. Though yield variability increased with intensification, there was no interaction with warming scenario. Risk and market analysis are needed to extend these results to understand implications for food security.

An experiment managed by an on-farm researcher was conducted in Sudan Savanna of three West African countries, Ghana (Vea), Benin Republic (Dassari), and Burkina Faso (Dano), in 2012. The experiment evaluated the effects of tillage practices and nitrogen fertilizer regimes on the yield of short-season maize Dorke SR variety for two landscape positions (upslope and footslope). A stripe-split plot design with four replicates at each of the three sites was used. Tillage practices (contour and along-slope ridges) were applied in the main plots, whereas nitrogen treatments (no nitrogen, 0 kg N ha−1; moderate nitrogen, 60 kg N ha−1; and high nitrogen, 120 kg N ha−1) were applied in the subplots of each landscape position. Both potassium and phosphorus fertilizers were applied at optimum rates. Grain yield and growth parameters showed diverse responses to the treatments across sites. The effects of slope position and nitrogen fertilizer regime on grain yield were significant (p < 0.05) across sites; the grain yield at the footslope position was 25% higher than that at the upslope, and the high nitrogen treatment resulted in a 140% increase in grain yield compared to no nitrogen condition. An insignificant (p < 0.05) increase in grain yield was observed for sites with contour tillage compared to sites with along-slope ridges. Leaf area index was not significantly (p < 0.05) affected by the treatments during tasseling across sites, and the values were consistent with increasing nitrogen levels. These results suggest that to optimize maize yield under subhumid conditions, farmers should concentrate maize cultivation in low-lying areas and follow the recommended fertilizer application regimes given current climate variability.

Conservation agriculture (CA) practices are being widely promoted in many areas in sub-Saharan Africa to recuperate degraded soils and improve ecosystem services. This study examined the effects of three tillage practices [conventional moldboard plowing (CT), hand hoeing (MT) and no-tillage (NT)], and three cropping systems [continuous maize, soybean-maize annual rotation and soybean/maize intercropping] on soil quality, crop productivity and profitability in researcher and farmer managed on-farm trials from 2010 to 2013 in northwestern Ghana. In the researcher managed mother trial the CA practices of no-tillage, residue retention and crop rotation/intercropping maintained higher soil organic carbon, and total soil N compared to conventional tillage practices after four years. Soil bulk density was higher under no-tillage than under CT soils in the researcher managed mother trails or farmers managed baby trials after four years. In the researcher managed mother trial, there was no significant difference between tillage systems or cropping systems in maize or soybean yields in the first three seasons. In the fourth season, crop rotation had the greatest impact on maize yields with CT maize following soybean increasing yields by 41% and 49% compared to MT and NT maize respectively. In the farmers’ managed trials, maize yield ranged from 520 – 2700 kg ha-1 and 300 – 2000 kg ha-1 for CT and NT respectively reflecting differences in experience of farmers. Averaged across farmers, CT cropping systems increased maize and soybean yield ranging from 23 to 39% compared with NT cropping systems. Partial budget analysis showed that the cost of producing maize or soybean is 20 – 29% cheaper with NT systems and gives higher returns to labor compared to CT practice. Benefit-to-cost ratios also show that NT cropping systems are more profitable than CT systems. We conclude that with time, implementation of CA practices involving NT, crop rotation, intercropping of maize and soybean along with crop residue retention presents a win-win scenario due to improved crop yield, increased economic return, and trends of increasing soil fertility. The biggest challenge however remains with producing enough biomass and retaining same on the field.

Loss of topsoil, enriched with nutrients, reduces soil fertility, and is one of the major impediments to sustainable crop production in West Africa. Appropriate management practices can lead to a stable restoration of land’s capacity to provide adequate ecosystem services. Thus, our study aimed to investigate the impact of alternative management practices and their interactions on topsoil (0–20 cm) organic carbon (SOCd), nutrient stocks [total nitrogen (STNd), phosphorus (SPd) and potassium (SKd)] under a maize-cotton rotation system on highly weathered soils of West Africa. To this end, on-farm trials were set up on four sites in the sub-humid Savanna of West Africa (2 in Benin (St1 and St2), and 2 in Burkina-Faso (St3 and St4)) in a strip-split plot layout, where 2 levels of tillage (contour ridge tillage, Ct and reduced tillage, Rt) were considered as main plot factor, and sub-plot factors included 2 levels of crop residue management (removed, CRr and incorporated, CRi), and 2 levels of N fertilizer (control, N0 and recommended rate, Nr). In 2016, after 5 cycles of annual maize-cotton rotation (2012–2016), the largest pool of soil nutrients was recorded on St3 (Haplic Lixisol, footslope in Benin), while the lowest content was observed on St1 (Ferric Lixisol, footslope in Burkina). When comparing the treatments, we found that Ct combined with CRi improved soil nutrient stocks in upslope sites, St2 (Eutric Plinthosol, upslope in Burkina) and St4 (Plinthic Lixisol, upslope in Benin), which are more prone to erosion. At the same time, footslope sites (St1 and St3) benefited from Rt coupled with CRi. CRi promoted an increase in SPd and SKd on all sites except St1 (Haplic Lixisol on footslope). The application of recommended dose of N fertilizer improved STNd under the Ct system in upslope regions and under the Rt system in footslope regions. However, no significant difference was observed for soil pH among the treatments across all sites. In summary, the efficiency of practices for conservation of soil nutrient stocks was closely related to landscape position of the field, which was correlated with soil moisture, textural class, and gravel content. Consequently, site-adapted tillage practices combined with residue incorporation are crucial for sustainable soil fertility management and crop productivity under maize-cotton rotation in smallholder production systems in West Africa.

Nitrogen (N) fertilizers applied to agricultural lands are often lost due to improper management practices. It is important to manage applied N fertilizers efficiently in order to promote sustainable crop production. In a two year (2013–2014) on-farm trial in the Sudan savanna of Benin (Dassari village) and Burkina-Faso (Dano village), we assessed the single and interactive effects of tillage and crop residue management on nitrogen uptake (NU) and nitrogen use efficiency (NUE) of cotton and maize in four different sites [S1 (Ferric Lixisol, footslope in Dano), S2 (Eutric Plinthosol, upslope in Dano), S3 (Haplic Lixisol, footslope in Dassari), and S4 (Plinthic Lixisol, upslope in Dassari)]. Two tillage practices, i) contour ridge tillage, and ii) reduced tillage, were considered as main plot factors, while the sub-plots consisted of two levels of crop residue management, i) with residue, and ii) without residue, and two levels of N fertilizer, i) control, and ii) recommended level of N fertilizer (45 kg ha−1 for cotton and 60 kg ha−1 for maize). We selected three indices, nitrogen fertilizer recovery efficiency (NFR), agronomic efficiency (AE), and partial factor productivity (PFPn) to describe the NUE of crops. Compared to reduced tillage, contour ridge tillage significantly improved NU and NUE indices of both cotton and maize on all sites except S3. When averaged across sites, implementation of contour ridge tillage instead of reduced tillage resulted in increase in NFR, AE and PFPn of cotton by 32.6%, 18.6%, and 20%, respectively. Also, NFR, AE, and PFPn of maize were increased by 29.4%, 25.8%, 1.7%, respectively under contour ridge tillage. Additionally, retention of crop residue significantly affected mainly NFR of cotton and maize, when averaged across sites. It increased NFR of cotton and maize by 14.6% and 14%, respectively, and enhanced NFR of cotton, yet not significantly on all sites. We concluded that increased soil N availability due to restricted horizontal soil water movement and improved soil water content is the primary contributor to increased NUE of both cotton and maize under the contour ridge tillage and crop residue retention across sites. However, such an effect was not notable on S3 as this site possesses improved soil hydrological properties a priori.

The effects of fertilization rate and water availability on peanut growth and yield of two cultivars were investigated in a series of field experiments at Bambey, Nioro and Sinthiou Malem in Senegal. Both rainy and dry season experiments were conducted over two years between 2014 and 2015, for a total of seven experiments. The first set of four experiments were to evaluate fertilizer application rate on peanut production. One experiment was conducted in the dry season 2014 in Nioro with four levels of fertilizer and one experiment in the rainy season 2014 in each of Bambey, Nioro and Sinthiou Malem with six levels of fertilizer in a RCBD with four replications both. The second set of experiments were to evaluate the effect of different water regimes on peanut production. Experiments were conducted in the dry season of 2014 and 2015 in Bambey and in Nioro 2015. The experimental design was a split plot design with four replications and three levels of water, namely, E, S1 and S2. The effects of fertilization rate on peanut in three different sites were not significantly different between fertilizer levels. However, irrigation treatments were significantly different in all sites during the two years. Under water stressed conditions, the seed yield was more affected than the biomass yield. Seed yield decreased by 33% when stress occurred at flowering period and by 50% when stress occurred during seed filling. The most sensitive period for yield declined was observed during the period of maturation followed to the flowering stage. The interaction between irrigation and fertilizer was not signification in both Bambey and Nioro sites of field experiments. Such experiments should be conducted in field based conditions where occur limited soil nutrients to test higher dose of NPK.