Optimizing the radiation synthesis and swelling of agar-based acrylate superabsorbent hydrogel for irrigation water conservation

This study reports the synthesis of novel agar/poly methacrylic acid/poly acrylic acid (AG/PMAc/PAc) superabsorbent hydrogels via gamma radiation and their subsequent urea modification to enhance swelling and water retention for agricultural applications. The superabsorbent hydrogels were prepared by irradiating aqueous mixtures of varying agar concentrations with methacrylic acid/acrylic acid (MAc/Ac) monomers, followed by urea treatment at different cycles and concentrations. The morphological characteristics and chemical structures were confirmed by SEM and FTIR, respectively. The maximum swelling occurred at 6 % agar and 1 % urea modification. Remarkably, the 1 % urea-modified hydrogel displayed a 41.1 % swelling increase and 236.4 % enhancement after the second modification cycle compared to unmodified samples. Water retention studies showed the modified hydrogel retained 53.2 % moisture after 14 days versus the complete drying of unmodified hydrogels. Soil application studies demonstrated the modified hydrogel increased moisture content by 177.3 % after 20 days, promoting better growth with 30 % more leaves and 38.9 % higher stem length in Vicia faba plants versus controls. This novel radiation-synthesized, urea-modified hydrogel with exceptional swelling and moisture retention capabilities shows promising potential for sustainable agricultural irrigation and crop productivity enhancement under water-deficit conditions.