Evaluation of a Natural Superabsorbent Polymer on Water Retention Capacity in Coarse-Textured Soils

Water availability, a vital factor in agriculture, is being threatened by shortages caused by droughts, desertification, and climate change. In this context, hydrogels, polymers with high water absorption and retention capacity, emerge as key solutions to improve water use efficiency in irrigation. This study investigated the effect of a natural superabsorbent hydrogel (TG) at different concentrations (0.3%, 0.5%, 0.8%, and 1.0%) on the water retention capacity in three coarse-textured soils and one medium-textured soil. Results are compared to an existing commercial polymer (COM). The evaluation shows that both polymers increase the values of the water retention curve; however, higher values were observed with TG. The addition of both hydrogels was compared in the increase of the available water capacity (AWC). For sand soil, the TG obtained a statistically significant difference of a 26% greater AWC when compared to the COM superabsorbent. Soils with a higher percentage of sand tend to obtain a greater improvement in the AWC. There is a proportional relationship of the increase in the AWC when increasing hydrogel concentration ($R^2$ = 0.74). Sand soil with a concentration of 0.5% of the TG showed 17.8% of the AWC, while for a concentration of 1.0% of this hydrogel, a value of 35.8% of the AWC was obtained. However, in soils with higher clay content, such as silt loam, the effect was smaller. Finally, the time required to reach a permanent wilting point (PWP) was compared. The loam sand soil increased the time to reach the PWP by more than three times using the TG or COM when compared to the same soil without any hydrogel concentration. In conclusion, the TG significantly improves water retention in coarse and medium-textured soils, making it a promising solution for improving water efficiency in agriculture, especially in drought-affected regions. However, additional field studies are needed to evaluate its long-term durability and environmental compatibility, ensuring its applicability under real agricultural conditions.