Biodegradable superabsorbent hydrogel for water holding in soil and controlled‐release fertilizer

ABSTRACT The bio‐based environment‐friendly functional polymers are the most desired materials for the society. Thus, a superabsorbent hydrogel (SAH) of starch‐modified poly(acrylic acid) was reported and the concentrations of reactants, initiators, and crosslinkers were optimized to achieve the highest water absorption (>700 g/g). The chemical structure of SAH was supported by solid‐state 13C nuclear magnetic resonance and Fourier‐transform infrared spectroscopic studies. The hydrogels were found to be biodegradable and possess high water absorption capacity. After the addition of 0.25% of the hydrogel, water‐holding capacity of the soil was enhanced by 120%. Significant effect was also observed on bulk density and porosity of the soil after the addition of SAH. Furthermore, urea‐encapsulated SAH can be used as a controlled release fertilizer for crops, as indicated by a preliminary study on the growth rate of chick pea (Cicer arietinum) plant. Thus, SAH has the potential to be used as a controlled‐release carrier and water‐conserving agent in different fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48495.