Nodulation and Growth of Cowpea in Response to Phosphorus, Cobalt, and Molybdenum Levels in Cerrado Soils

Cowpea production potential often falls short, despite the crop's efficiency as a legume. This underperformance is primarily attributed to widespread deficiencies of phosphorus (P), cobalt (Co), and molybdenum (Mo) in Brazilian soils, especially in the Cerrado region. This study aimed to determine the optimal doses of P, Co, and Mo to enhance cowpea nodulation, biological nitrogen fixation, and overall plant growth. Two greenhouse exper-iments were conducted using a randomized complete block design in a 2 × 5 factorial scheme (two soils and five doses of each nutrient, inoculated with strain BR 3262), with four replicates. In Trial I, P₂O₅ doses of 0, 100, 200, 300, and 400 mg pot⁻¹ were tested, while in Trial II, Co:Mo ratios (w:w) were evaluated: 0:0, 2:8, 3:16, 4:32, and 6:64 (mg pot⁻¹). The variables analyzed included phytotechnical parameters. The application of 200 mg pot⁻¹ of P₂O₅ (200 kg ha⁻¹) resulted in the highest nodulation, nitrogen accumulation, and increased cowpea biomass. Furthermore, medium-high micronutrient levels (Mo at 32 g ha-1 and Co at 4 g ha-1) provided superior nodulation, biomass, and nitrogen accumu-lation. Adequate P and micronutrient fertilization is essential for plant development, rein-forcing its pivotal role in maximizing cowpea productivity under Cerrado soil conditions.