Enhancing Plant Growth of Vigna radiata Using Biodegradable Superabsorbent Carboxymethylcellulose Nanohydrogel Enriched with Carbon Dots under Water-Stressed Conditions

Worldwide water paucity and increasing food demand have stressed the agricultural sector for developing strategies to enhance quantity and quality of crop production with limited water resources. In order to pursue a solution of this demand, an efficient, resilient, sustainable, biodegradable, superabsorbent N–S–P carbon dots enriched carboxymethylcellulose nanohydrogel (CDs@CMC nanohydrogel) has been fabricated to study the growth pattern of Vigna radiata with limited water supply in a pot experiment. Characterization techniques like FTIR, TGA, and FESEM analysis established the morphology and structural characteristics of the prepared hydrogel. Sequential variation in the weight % of soil CDs@CMC nanohydrogel ratio was done to study the swelling ratio, water holding, and retention capacities of soil. Further, to ascertain their behavior as soil conditioners during plant growth, these were coupled with varying amounts of N–S–P carbon dots to give Gel-1, Gel-2, and Gel-3. The swelling ratios of Gel-1, Gel-2, and Gel-3 were found to be 2206%, 2582%, and 2712%, respectively, at pH 4, and their water holding capacities were calculated to be 36.7%, 39.5%, and 41.2%, respectively, with 1 wt % of each gel mixed with 50 g of soil, which is higher as compared to 50 g of soil alone (21.2%). The water retention time of the soil increased from 5 to 12 days with the soil mixed hydrogel at room temperature. The hydrogel remained intact, and their swelling capacity shows a slight decline after each consecutive water absorption–release cycle for ten cycles. Further, the seedlings grown in a potting mix containing Gel-1, Gel-2, and Gel-3 survived better than soil, but the best results were shown by Gel-2 with 1 wt % of hydrogel mixed with soil due to the incorporation of a suitable amount of N–S–P CDs in the hydrogel matrices. The ANOVA analysis is also applied for the optimization of the growth parameters of the growth pattern of Vigna radiata, and the study results are supported with the batch studies. Therefore, the environmentally safe, versatile N–S–P carbon dots enriched carboxymethylcellulose nanohydrogel holds promise for sustainable farming applications under water-limited conditions in arid and semiarid regions.