Novel fabrication of biodegradable superabsorbent polymer from wheat stalk for water holding and sustained fertilizer release

Abstract

Water-retaining agents have been shown to significantly improve the efficiency of irrigation water use in long-term agricultural activities, outperforming traditional irrigation methods. However, existing water-retaining agents still face challenges related to cost-effectiveness and degradability. To address these issues, we developed a superabsorbent material composed of wheat stalk (WS) and polyacrylic acid (PAA)–polyacrylamide (PAM), fabricated via versatile polymerization techniques. The integrated properties of the material, including water absorbency, water holding capacity, urea sustained-release behavior, and soil degradation, were thoroughly evaluated. The results indicated that WS/PAA–PAM exhibited a water absorption capacity of 273.54 g g⁻¹ in deionized water and 44.54 g g⁻¹ in saline solution, demonstrating excellent water retention properties. Kinetic studies revealed that water diffusion followed Fick diffusion, and the swelling process could be described by a first-order kinetic model. Notably, the material maintained high water absorption even after three cycles of re-swelling. Furthermore, WS/PAA–PAM effectively controlled the release of urea, minimizing fertilizer loss due to runoff, thereby promoting sustained nutrient delivery. These findings highlight the potential of WS/PAA–PAM as a cost-effective, biodegradable water and fertilizer management solution, offering a promising strategy for improving water and fertilizer utilization efficiency in future agricultural applications.