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

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 13 C 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.