Starch derivative-based superabsorbent with integration of water-retaining and controlled-release fertilizers

► The synthetic superabsorbent is based on sulfonated corn starch. ► The superabsorbent integrates water-retaining and controlled-release fertilizers. ► The maximum swelling capacity: 498 g g−1 (water), 65 g g−1 (0.9 wt.% NaCl solution). ► The synthetic superabsorbent polymer is biodegradable. ► The starch sulfate could improve the phosphorus release greatly.