Tobi Moriaque Akplo

To restore soils degraded by unsuitable practices, which have led to declines in organic matter content and associated consequences, sustainable land management (SLM) practices have been implemented in central Benin. This study aimed to evaluate the effects of these practices on soil organic matter (SOM) levels in cultivated soils in Central Benin. Soil samples were collected from a depth of 0 to 20 cm on SLM plots in two agricultural areas: N’Tchon and Odjobilè. The SLM practices studied were maize intercropped with pigeon pea ( Cajanus cajan ), mucuna ( Mucuna pruriens ), soybean ( Glycine max ), cowpea ( Vigna unguiculata ), groundnut ( Arachis hypogea ), aeschynomene ( Aeschynomene histrix ), and cassava ( Manihot esculenta ). For each SLM practice, adjacent control plots were sampled. Soil pH, cation exchange capacity (CEC), soil organic carbon (SOC), carbon organic stock (COS), and particulate organic carbon (POC) were measured. Compared to the adjacent control plots, the soybean–maize and aeschynomene–maize rotations significantly increased soil CEC ( p < 0.05). SOC differed significantly ( p < 0.05) among SLM practices, ranging from 0.37 to 1.67 g/kg. COS was higher with pigeon pea–maize intercropping (37.21 Mg C ha ⁻¹ ) in Odjobilè and with cassava–maize intercropping (37.46 Mg C ha ⁻¹ ) in N’Tchon. The contribution of coarse particulate organic carbon (cPOM‐C) to total particulate organic carbon (tPOM‐C) was smaller than that of fine particulate organic carbon. The greatest cPOM‐C was observed with cowpea–maize and pigeon pea–maize intercropping. However, the greatest fPOM‐C was observed with cowpea–maize intercropping in Odjobilè and with pigeon pea–maize intercropping in N’Tchon. Therefore, SLM practices, such as intercropping with pigeon peas and maize, can serve as an alternative to crop residue burning. These practices can help restore the fertility of degraded soils.

This study investigated the effect of conservation agriculture (CA) practices (e.g. no-tillage (NT) and maize-soybean (MS) intercrops) on the yield and profitability of maize and cotton within the first two years of a crop rotation system. A factorial design that compared two tillage practices (conventional tillage, CT and NT) and two cropping systems (sole maize, M and MS) was implemented on an experimental station in Northern Benin. All treatments were replicated thrice in 2022 and 2023. Soybean yield, maize grain yield and yield components, and seed-cotton yield and yield components were measured. Gross margin, labour productivity, and benefit:cost ratio were calculated, and a sensitivity analysis was done on the economic indicators under five scenarios (S0: gross margin calculation based on actual costs; S1: 30% higher fertiliser price; S2: 30% lower fertiliser price; S3 and S4, respectively: considering +/−1 standard deviation to the maize grain + soybean and seed-cotton yield). Tillage options and cropping systems significantly affected maize and cotton performance, but effects tended to vary between seasons. Treatment NT+MS produced the highest grain yield (4487 kg ha^–1) and rain use efficiency (4.12 kg mm^–1) in 2022, while CT+M produced the highest grain yield (3195 kg ha^–1) and rain use efficiency (2.84 kg mm^–1) in 2023. In the case of cotton, NT produced higher seed-cotton yield (1720 kg ha^–1), boll number (7.38 bolls/plant), and rainfall use efficiency (1.56 kg mm^–1) compared to CT in 2022. In 2023, cotton preceded by maize-soybean intercrops (NT+MS and CT+MS) produced significantly higher yield, aboveground and belowground biomass than cotton preceded by sole maize (NT+M and CT+M). For maize plus soybean, treatment NT+MS resulted in a significant increase in the gross margin, with an average of 582 US$ ha^–1 with respect to CT+M under all scenarios in 2022, whereas CT+M and NT+MS attained a significantly higher maize/soybean gross margin in 2023. In the case of cotton, NT increased gross margin by 90-314% compared to CT across the sensitivity analysis scenarios in 2022. In 2023, cotton preceded by MS intercrops (NT+MS and CT+MS) showed a higher gross margin than preceded by sole crops (NT+M and CT+M) across all scenarios. To the well-documented effects of diversification on crop productivity, this study adds evidence on its positive impact on economic performance in a West African context. On-farm research and rural extension are necessary to further fine-tune these practices to fit the reality of smallholder cotton-based cropping systems of Benin.

Phosphorus (P) is an essential macronutrient for plant growth and development. However, most of the P in the Earth's crust is insoluble, making it inaccessible to plants. This review examines the ability of phosphate-solubilizing microorganisms (PSMs) to convert these insoluble forms of P into plant-accessible forms, highlighting their potential use as biofertilizers. PSMs mainly consist of phosphate-solubilizing bacteria and fungi, which play crucial roles in the soil P cycle. The mechanisms of P solubilization encompass not only the key components of the soil P cycle but also relate to PSM species and the presence of phosphatase/phosphohydrolysis-related genes. Organic P are mineralized by enzymatic activity, while inorganic P, such as iron-phosphate, aluminium-phosphate, and calcium-phosphate are solubilized through organic acid production, proton extrusion, siderophore secretion, and exopolysaccharide production. Additionally, arbuscular mycorrhizal fungi are among the PSMs that effectively enhance P uptake in plants. Using PSM inoculants as biofertilizers has shown promise in improving soil P availability. However, further research is needed to determine the optimal application conditions, including timing, inoculum forms, and dosages, to maximize their effectiveness.

The lack of soil fertility is one of the main constraints for oil palm production. In Benin, scientific research has been conducted to address this problem. This article summarizes the scientific work conducted in Benin so far on soil fertility management in oil palm grove. To produce this review, we used peer‐reviewed articles and references. It has enabled us to categorize the various works on soil fertility in Benin palm plantations into three categories, which include works on the management of organic matter, works on the association of oil palm with annual food crops, and works on the management of mineral fertilization. From all these studies, apart from climatic factors, the major constraint affecting oil palm production is potassium (K) deficiency. But boron (B) is also mentioned in the scientific literature as a parameter requiring particular attention, whose deficiency leads, in addition to K, to enormous production losses. It would therefore be advisable to direct future research toward alternatives that take into account climatic variability and the mineral nutrition of oil palm in K and magnesium (Mg), while ensuring good management of soil organic matter to ensure the sustainability of oil palm‐based production systems.

Across the semiarid regions of West Africa, cowpea ( Vigna unguiculata (L.) Walp) varieties grown by farmers are either grain‐ or forage‐only, and often fields are not fertilized. Information regarding profitability of dual‐purpose over traditional varieties and fertilizer application in cowpea production system is limited. The main objective of this study was to quantify the economic value of newly released dual‐purpose and forage cowpea varieties and fertilizer inputs across the Senegalese peanut basin. This field study was conducted across three locations in Senegal (Bambey, Boulel, and Darou Mousty) in 2021 and 2022. Treatments were 20 cowpea varieties in the main plot and two levels of fertilizer (an unfertilized control and fertilized) in the subplot. Cowpea varieties E‐BC4STR1, E‐BC4STR5, E‐BC4STR11, Kelle, and Melakh had relatively greater grain yields (average 429–474 kg ha ⁻¹ ) in all environments. Forage varieties 66‐35F and 58‐74F produced the most forage (average 2353 and 1717 kg ha ⁻¹ ) yields across environments. Fertilizer‐NPK application increased grain yield by 22%–40% in most environments. Unlike grain yield, varietal effects on forage yields occurred only with fertilizer application. Dual‐purpose cowpea varieties E‐BC4STR1, E‐BC4STR2, E‐BC4STR5, and E‐BC4STR11 had a stable, significant economic value in our study compared with grain‐only variety Yacine (traditional variety) or forage variety 66‐35F. Fertilizer‐NPK increased net revenue in four out of six environments. We conclude that using dual‐purpose cowpea varieties provided significant economic advantage over traditional varieties, and application of fertilizer further increased the economic value. However, further studies are needed to determine the economically optimal fertilizer rate.

Soil erosion has become one of the most common environmental problems and threatens food security. This study assessed the short‐term effect of tillage and mulch on soil redistribution using the beryllium‐7 method, soil moisture distribution, and soil organic carbon loss through soil erosion in typical agroecological conditions of Benin. The experiment was conducted on acrisols (at Dan) and ferralsols (at Za‐zounmè) in central Benin. Three tillage practices slope ridging (SR), contour ridging (CR), and no‐tillage (NT), and three mulch doses 0 (0 M), 3 (3 M), and 7 t ha⁻¹ (7 M) on soil erosion under maize were investigated. The results showed a tillage and mulch interaction significantly (p < 0.05) influencing the soil redistribution, the loss of total carbon, the carbon of the particulate organic matter (C_POM), and the carbon content of the fine organic matter (C_MOM). High soil erosion was observed under SR0M (−10.19 t ha⁻¹) at Dan and under NT0M (−7.36 t ha⁻¹) at Za‐zounmè. NT7M (0.80 t ha⁻¹), SR7M (0.69 t ha⁻¹), CR3M (2.07 t ha⁻¹), and CR7M (4.05 t ha⁻¹) showed deposition at Dan, while SR7M (0.23 t ha⁻¹), NT7M (1.69 t ha⁻¹), and CR7M (3.93 t ha⁻¹) showed deposition at Za‐zounmè. C_MOM was lost on both sites. Mulch increases soil moisture for all three tillage treatments, and this effect is well pronounced especially if the amount of mulch is great. This study revealed useful information to be taken into consideration when developing soil and water conservation management strategies in Benin.

Addressing the challenges of food and nutrition insecurity in sub‐Saharan Africa will require innovative agriculture production systems that support multiple objectives. Dual‐purpose cowpea [Vigna unguiculata (L) Walp] varieties are expected to offer greater grain yields for human consumption and high‐quality fodder for livestock in semiarid regions of Senegal. However, limited information is available on the effects of varieties and fertilizer on dual‐purpose cowpea. The main objective of this research was to evaluate the grain and fodder yield of five newly released cowpea varieties (Kelle, Leona, Lizard, Sam, and Thieye) compared to traditional variety (Yacine) with fertilizer (nitrogen‐phosphorus‐potassium 6‐20‐10) and no‐fertilizer application. Genotype × environment × management experimentations were conducted across three cowpea production zones of Darou Mousty (400 mm per year), Bambey (500 mm per year), and Boulel (700 mm per year) over three growing seasons (2019–2021) to compare the growth and yield parameters of the cowpea varieties. Results of the study showed a 40% grain yield advantage from the greater yielding (Leona) variety in this study compared with the lower yielding (Lizard) variety. There was an additional 22% grain yield increase from the application of fertilizer compared with the unfertilized treatment. The variety (Leona) that produced the most grain also produced the most fodder yields. There was 67% fodder yield advantage from Leona compared with fodder yield from the older variety Yacine. Across varieties, application of fertilizer increased fodder yield by 15% compared to the unfertilized control. Average grain yield in high‐yielding environment (Boulel 2019, Darou Mousty 2019, and Bambey 2021) was 100% greater compared with average grain yield in low‐yielding environments (Boulel 2021, Darou Mousty 2021, and Bambey 2019). Compared to Yacine, dual‐purpose varieties increased net returns by 15%–58% or 13%–42% with early‐ and late‐season cowpea sales, respectively. However, fertilizer application was profitable only when cowpea grain and fodder were sold later in the season. In general, cowpea number of branches, pod number, and pod yield increased with fertilizer application. We concluded that producers can adopt dual‐purpose varieties and proper fertilizer management to increase grain yield, fodder availability, and profitability of cowpea production in Senegal.

Growing cowpea (Vigna unguiculate (L) Walp) in rotation with millet (Pennisetum glaucum (L.) R. Br.) can increase millet productivity through biological nitrogen fixation. However, in Senegal, legume crop residues are generally removed for livestock feed, and little information exists on how burying the residue instead of removal affects the subsequent crop yield. This study assessed the productivity of cowpea varieties and evaluated prior cowpea residue management effect on grain and biomass yield of millet (Pennisetum glaucum (L.) R. Br) in rotation. Experiments were conducted in the National Center for Agronomic Research (CNRA) of Bambey in Senegal from 2020 to 2022. Treatments include 20 cowpea varieties, two fertilizer rates, and cowpea residue management practices (residue removal vs. burying) in a split‐split plot arrangement. Results showed that fertilizer and variety had significant effect on grain and fodder yields of cowpea. Cowpea fodder nutrient concentrations differed by variety, and the superior cowpea variety, 66‐35F, in nutrient concentration in this study had a 2.8‐0.45‐0.82% N‐P‐K. Applying fertilizer to previous cowpea crop increased millet grain yield by 63% compared to millet yield following previous non‐fertilized cowpea plots. Furthermore, incorporation of cowpea residue prior to millet planting increased millet yield by 40% compared with the removal of cowpea biomass in 2020 but had no significant effect in 2021. In general, the amount of cowpea biomass buried had significant positive relationship with millet grain yield. Across years, millet grain yield increased by 0.16 kg ha⁻¹ for each kilogram per hectare increase in cowpea biomass buried prior to millet planting. Results showed that a minimum of 1500 kg ha⁻¹ cowpea buried biomass was required to increase the probability of millet grain yield above 1000 kg ha⁻¹. We concluded that the previous year's cowpea residue burial and fertilizer management improved productivity of the rotational millet crop.

Addressing the challenge of food and nutrition insecurity in Sub‐Saharan Africa (SSA) will require innovative agriculture production systems that support multiple objectives. In recent years, several high‐yielding, and nutrient‐dense varieties of cowpea (Vigna unguiculata (L.) Walp), pearl millet (Pennisetum glaucum (L.) R. Br.), and sorghum (Sorghum bicolor (L.) Moench) have been developed purposely as dual‐purpose (DP) varieties in SSA to meet human nutrition and livestock feed needs. This review synthesized published data on DP varieties from cowpea, pearl millet, and sorghum. Findings showed that DP crops and varieties were largely grown by smallholder farmers in a variety of soil and climatic conditions with production systems characterized by large gaps between attainable and actual crop yields which varied significantly among regions. While the grain and fodder yield of traditional varieties (TV) of cowpea averaged 700 kg ha⁻¹ and 860 kg ha⁻¹, respectively, the reported grain yield of DP varieties was 1100 kg ha⁻¹ and 2150 kg ha⁻¹ for fodder. The average grain yield of TV millet varieties was 750 kg ha⁻¹ and 2500 kg ha⁻¹ for fodder. Similarly, average grain yield for DP millet varieties was 2000 kg ha⁻¹ and 4200 kg ha⁻¹ fodder. Dual‐purpose sorghum varieties yielded greater grain (>3000 kg ha⁻¹) and fodder (3500 kg ha⁻¹) compared to TV. Little data were obtained on the nutritive qualities of cowpea, millet, and sorghum DP varieties. However, DP millet varieties were reported to be more digestible than TV varieties. Furthermore, adoption of DP varieties improves fertilizer use efficiency, profitability, environmental sustainability, and resilience of the whole farm system compared to TV. Considering fertilizer's high prices, availability, and quality in semi‐arid countries in addition to farmer poverty level, economic evaluation and environmental impact assessment are critical before wide dissemination.

Climate forecasts show increased frequency and intensity of drought in the semi-arid regions of west Africa, which negatively impacts food and nutrition security. Developing and improving resilient cropping systems will require adequate varieties with improved agronomic practices. The purpose of the study was to evaluate grain and biomass production of newly released dual-purpose millet varieties under different fertilizer rates and planting densities across the millet-cropping regions of Senegal with different rainfall regimes (Bambey: 600 mm, Boulel: 700 mm, Nioro: 650 mm, and Sinthiou Malème: 800 mm). The experimental design was a split-split-plot with three replicates using one traditional variety (Souna 3) and four dual-purpose varieties (Thialack 2, SL28, SL 169, and SL423) as the main factor; two planting densities (E1: 12,500 seed hills ha⁻¹ and E2: 25,000 seed hills ha⁻¹) as second factor; and eight fertilizer combination as sub-sub-plots. Results showed that variety yield response differed with environments. Regardless of variety, increasing sowing density increased grain yields (1600 kg ha⁻¹ for E2 vs. 1000 kg ha⁻¹ for E1) and fodder yields (4200 kg ha⁻¹ for E2 vs. 3100 kg ha⁻¹ for E1). Fertilizer response differed between environments, but the application of 70N–10P–19K + 2.5 t ha⁻¹ cow manure produced appreciable yields in all the environments. The dual-purpose varieties (SL 28, SL 169, and Thialack 2) sown at E2 produced the best grain and fodder yields. Soil water content was greater for all varieties (Thialack 2: 12.32%; Souna 3: 5.32%; SL28: 6.32%; and SL423: 9.23%) at higher planting density compared with normal density (Thialack 2: 9.25%; Souna 3: 3.21%; SL28: 5.43%; and SL423: 7.47%). The highest agronomic-use efficiency (AEg) of inorganic fertilizer applied was observed at 25,000 seed hill ha⁻¹ and averaged 6.63 kg kg⁻¹ at Boulel, 9.20 kg kg⁻¹ at Sinthiou Malème, 4.67 kg kg⁻¹ at Bambey, and 8.32 at Nioro kg kg⁻¹. The AEg significantly varied among fertilizer combinations, with greatest AEg obtained with 70N–22.5P–22.5K (5.53 kg kg⁻¹) at Boulel and with 95N–17P–27K (4.66 kg kg⁻¹) at Bambey. This study provides crop-management options for millet-cropping systems in the semi-arid regions of west Africa for improving millet productivity while enhancing system resilience through better conservation and utilizing of soil water.