Túlio William da Silva Gonçalves

Global climate change has intensified prolonged droughts, making the development of sustainable agricultural technologies essential. Although potassium humate (KH) and Bacillus aryabhattai (BA) are recognized individually as effective biostimulants, their joint application represents an innovative, unexplored complementary strategy to mitigate drought stress in cowpea (Vigna unguiculata L. Walp.). This study aimed to evaluate the effects of these bio-inputs on mitigating water stress in the cowpea (Vigna unguiculata L. Walp.) cultivar ‘BRS Verdejante’. The experiment was conducted under greenhouse conditions using a completely randomized design in a 2 × 8 factorial arrangement, with two water regimes (100% and 50% crop evapotranspiration—ETc) and eight biostimulant combinations of KH and BA. While BA alone (T4) intensified osmotic adjustment via proline accumulation and APX activation, the combined treatment T5 (10 mg kg⁻¹ soil KH + 4 mL kg⁻¹ seed BA containing 1 × 10⁸ CFU mL⁻¹) achieved the best overall performance under drought (50% ETc). T5 effectively enhanced superoxide dismutase activity, preserved leaf relative water content, and reduced cell membrane electrolyte leakage by 42.6% compared to untreated stressed plants. These physiological adaptations protected reproductive organs, resulting in a 51.6% increase in pod number per plant under drought. The strategic co-application of low-dose potassium humate (10 mg kg⁻¹ soil) and B. aryabhattai (4 mL kg⁻¹ seed) effectively regulates osmotic and oxidative homeostasis, maintaining pod formation (+51.6%) and securing cowpea grain yield per plant under drought stress, thus serving as a promising strategy to mitigate drought stress in cowpea under controlled greenhouse conditions.

This study investigated whether foliar application of silicon (Si) and methionine (Met) can modulate the biochemical metabolism and growth of cowpea ‘BRS Exuberante’ during water restriction and rehydration cycles, based on the hypothesis that these elicitors could improve physiological recovery after water stress. Considering the above, the experiment was conducted in a completely randomized design, in a 2 × 4 factorial scheme, with four replications. The factors studied were: water stress period and rehydration period. In addition, the following foliar doses of the elicitors were applied: control, 300 mg L-1 of Si, 890 mg L-1 of Met, and the combination of both, 300 mg L-1 of Si + 890 mg L-1 of Met. The results that positively impacted the mitigation of water stress observed in the presence of silicon were more related to growth, although they also reflected improvements in biochemical metabolism. Methionine, on the other hand, was associated with changes in biochemical aspects that benefited growth. In both cases, the improvements that occurred during water restriction were what enabled greater recovery potential after rehydration. Both attenuating agents proved effective in inducing tolerance to certain physiological characteristics. Therefore, their use represents a promising alternative to strengthen the tolerance mechanisms of cowpea, especially by stimulating its ability to recover from stress after rehydration.