Evaluation of the effects of hydrogel and glycine betaine application on growth, physiological characteristics and yield of peanut under water deficit

The main objective of all countries, particularly those in dry regions, is to preserve water resources. This study addresses the knowledge gap regarding effective strategies to mitigate drought-induced damage and enhance productivity in peanut plant. Accordingly, during two summer seasons of 2023 and 2024, a field trial was conducted to investigate the impact of hydrogel addition to sandy soil and foliar spraying of glycinebetaine (GB) on physiological parameters, growth, yield, its components, and nutrients of peanut seeds subjected to water deficit stress. Water deficit (75% of the water irrigation quantity, WIQ) resulted in reduced levels of chlorophyll a, chlorophyll b, carotenoids, indole acetic acid (IAA), growth, seed yield, oil, carbohydrates, and protein in the yielded seeds compared to normal irrigation (100% WIQ). However, hydrogel treatment or GB treatment alone or in combination showed a stimulatory effect on growth criteria and yield attributes of peanut plants under 100% WIQ and 75% WIQ via improving chlorophyll a, chlorophyll b, carotenoids, IAA, total soluble sugars and phenols. Hydrogel soil addition with GB foliar treatment exhibits more increases in the above-mentioned parameters over hydrogel or GB treatment alone under 100% and 75% WIQ. Additionally, 20 mM GB with hydrogel 80 kg ha-1 worked better over other treatments, as it caused the highest values of increases in most studied parameters. It increased seed yield (ton ha-1) and biological yield (ton ha-1) under 100% WIQ by 72.45% and 78.92% and under 75% WIQ by 141.37% and 112.97% respectively. These results show that GB, when combined with hydrogel polymer, significantly improve drought tolerance in peanut, providing a viable strategy to increase crop yields in water-limited environments. In view of climate change, this study emphasizes the potential of combining hydrogel with GB for sustainable agricultural practices.