Cultivo de Feijão-caupi sob escassez hídrica no semiárido: estratégias de irrigação e uso de bioinsumos na mitigação do déficit hídrico

Abstract

Water deficit affects plant physiological processes; consequently, water management becomes essential under conditions of water scarcity. Deficit irrigation is a viable option for situations of limited water availability without compromising productivity. Additionally, the use of bioinputs—particularly plant growth-promoting bacteria—is increasingly common for mitigating the effects of water deficit. Understanding the interactions between cowpea and these growthpromoting bacteria, combined with deficit irrigation strategies in semi-arid regions, facilitates decision-making regarding crop management under water-limited conditions, aiming for efficient water use. Thus, this study was divided into two chapters: the first aimed to evaluate leaf gas exchange and yield parameters of cowpea inoculated with Bacillus aryabhattai and coinoculated with Rhizobium tropici under different deficit irrigation strategies; the second aimed to evaluate the potential to mitigate water deficit in cowpea cultivation through inoculation with growth-promoting bio-inputs combined with deficit irrigation strategies in a semi-arid region. he experimental design was a randomized complete block in a split-plot arrangement with four replications. Deficit irrigation management treatments were assigned to the main plots (IP – full irrigation; IDC50% – deficit irrigation during vegetative growth; IDFR50% – deficit irrigation during flowering and grain formation; IDE50% – deficit irrigation during grain filling; IDR50% – deficit irrigation throughout the entire cycle), while growth-promoting bio-input treatments were assigned to the subplots (TS1 – inoculation with B. aryabhattai; TS2 – co-inoculation: B. aryabhattai + R. tropici; TS3 – positive control with nitrogen fertilization; TS4 – negative control without nitrogen fertilization or inoculants). he growth-promoting bio-inputs used in the experimental trials were the bacteria Bacillus aryabhattai (CMAA 1363, at a concentration of 1 × 10⁸ CFU mL⁻¹) and Rhizobium tropici (SEMIA 4077 and 4088, at a concentration of 3 × 10⁹ CFU mL⁻¹). Water deficit was established at 50% of local crop evapotranspiration (ETc). A localized drip irrigation system was used, featuring emitters with a flow rate of 1.6 L h⁻¹ spaced 0.30 m apart. Irrigation was managed on a daily basis, with application depths calculated using a Class A pan. The variables analyzed included gas exchange, production parameters, water productivity, the water deficit sensitivity coefficient, economic analysis, and the economic productivity of irrigation water. The results demonstrate that combining deficit irrigation strategies with growth-promoting bio-inputs can improve physiological performance, cowpea yield, and crop profitability under semi-arid conditions.