The Impacts of Applying Cobalt and Chitosan with Various Water Irrigation Schemes at Different Growth Stages of Corn on Macronutrient Uptake, Yield, and Water Use Efficiency

While previous studies have demonstrated the positive effects of low cobalt (CB) levels and chitosan (CH) on yield and nutrient status, information about their individual and combined applications on plants under stress is still lacking. Therefore, we conducted a study to investigate CB and CH impacts on mitigating water stress during growth stages and their effects on corn macronutrient uptake and yield. Four irrigation schemes were employed, including (1) control (full irrigation), (2) 70% of irrigation water during the vegetative stage, (3) 70% of irrigation water during the flowering stage, and (4) 85% of irrigation water during both the vegetative and flowering stages. The plants were treated with (7.5 mg l−1) CB injected into the irrigation water and CH foliar application (500 mg l−1), while distilled water was used as the control. Plants that were exposed to water stress during the flowering stage and treated with CB, or those subjected to water stress during the vegetative stage and treated with CH, showed increased macronutrient uptake and growth, which had a positive effect on yield and water use efficiency. However, when CB and CH were applied in combination, their potential to enhance these features depended on the pattern of water stress adopted. Overall, the application of CB and CH was effective in mitigating water stress, and their combined application was particularly effective when 70% of irrigation water was applied during the flowering stage. This approach resulted in the highest yield, macronutrient uptake, water use efficiency, and tolerance index.