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.

This study evaluated the long-term effects of a single application of different biochar types and quantities in combination with cow manure and annual inorganic fertilizer on soil properties and grain yield under millet monocropping and millet–peanut rotation in sandy soils of the peanut basin of Senegal. Results of over six years showed that a single application of 5–10 t ha⁻¹ biochar (rice husk or Typha australis) and/or manure significantly increased soil pH (from 5.5 to 6.3) and total C (from 1.84% to an average of 2.69%). Soil available P increased due to all treatments. These improved soil properties were maintained for at least eight years following a single application of 5–10 t ha⁻¹ biochar and/or manure. There was limited or slightly negative effects of biochar application on soil N and total soil microbial activity. Applications of either one-third or half of national recommended NPK rate, in combination with a single application of biochar or cow manure, increased millet grain yield up to four to five times (i.e., 100 to 450 kg ha⁻¹), which was equivalent to the yield of treatments receiving the full national recommended fertilizer rate. Limited improvement was observed on peanut yield. This research clearly shows the synergistic benefits of applying single low rates of organic materials in combination with annual low levels of inorganic fertilizer. Treatments receiving the national recommended inorganic fertilizer rates (150 kg ha⁻¹ NPK 15-15-15 and 100 kg ha⁻¹ of urea four weeks after planting) did not produce more than 400 kg ha⁻¹. Biochar application alone did not increase millet yields. With a recommended biochar application rate of 5 t ha⁻¹, we calculate that Senegal has enough biomass available for biochar to cover all of its cropland every 4.4 to 5.5 years. Of particular importance, the 0.85% increase in stable total C has the potential to sequester 27.2 tons C ha⁻¹ and if scaled across Senegal’s 1.6–2.0 million ha of peanut and millet cropland, this practice could sequester 43.52 to 54.4 million tons of C having mutual benefits on crop productivity and climate change mitigation.

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.

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.