Growth, Physiology and Yield of Traditional Cowpea Varieties Under Salt Stress Using Exogenous Magnesium

Salinization is one of the main environmental challenges affecting agriculture in semi-arid regions. We evaluated the feasibility of foliar magnesium and its effects at different doses on the acclimation of cowpea varieties under salt stress. The experiment occurred in a greenhouse using a randomized block design in a 2 × 3 × 4 factorial scheme, with five replicates. Two cowpea varieties-'Pingo de Ouro' and 'Costela de Vaca'-were subjected to three salinity levels in irrigation water (0.54, 3.50, and 5.00 dS m^-1) and four foliar magnesium (Mg) doses (0, 1, 2, and 3 mL L^-1). Under 3.50 dS m^-1 salinity, the 1 mL L^-1 dose resulted in the highest yield per plant (18.29 g). CO₂ assimilation was highest with 2 mL L^-1 Mg at 3.50 dS m^-1 for 'Costela de Vaca', and with 1 mL L^-1 Mg at 5.00 dS m^-1 for 'Pingo de Ouro'. The 'Pingo de Ouro' variety was more tolerant to 'Costela de Vaca'. Foliar Mg fertilization proved to be a promising strategy to mitigate the effects of salt stress in cowpea, especially for 'Pingo de Ouro'. Magnesium effectively reduces salt stress, but its effect varies by plant variety and irrigation salinity, necessitating customized dose adjustments.