Starch-based biodegradable hydrogel as seed coating for corn to improve early growth under water shortage

In this work, the effect of a biodegradable hydrogel as a seed coating on the early growth of corn seed was studied. The hydrogel was a succinate-modified potato starch, and it had an equilibrium water absorption capacity of 260 g distilled water (DW)/g hydrogel. To coat corn seeds, the seeds were slightly wetted with an aqueous adhesive solution and then, in a closed container, mixed with a dry mixture of the modified starch (MS), bentonite, and talc. The damp coated seeds were air-dried at 40 degrees C for 24 h. The seed emergence and postemergence growth of coated and uncoated seeds were assessed with respect to: (1) the amount of MS on coated seeds, and (2) the available water supply. At a water supply of 77% field capacity (FC), the coated seeds showed a significantly higher rate of emergence than uncoated seeds-however, only a minor improvement was observed at higher and lower water supply levels (92, 82, and 65% FC, respectively). This indicates that, while poor water absorption by hydrogel at low water supply (65% FC) has limited benefit to seed water availability, the effect of good water retention by the hydrogel at high water supply (92, 82% FC) appears redundant in the presence high soil water availability. After 14 and 21 days of growth, the dry weights of the corn plants' roots and shoots did not significantly differ between coated and uncoated seeds, which indicate that, after seed emergence and root development, the contribution of the hydrogel coating to the plant's water requirements becomes negligible. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48523.