Superabsorbent Hydrogel Composite Based on Starch/Rice Husk Ash as a Soil Conditioner in Melon (Cucumis melo L.) Seedling Culture

A superabsorbent hydrogel composite based on a starch-grafted-poly(sodium acrylate) matrix filled with husk rice ash (RHA) was synthesized and tested as a soil conditioner to enhance the melon seedling growth. The incorporation of 20 wt% of RHA in the hydrogel matrix endowed the composite with an outstanding liquid uptake capacity (42,000%). Field experiments were performed to investigate the effect of the amount of hydrogel, type o subtract (sandy soil and coconut fibers) and type of soil (sandy soil and clay soil) on several parameters related to the plants' growth process. Overall, the plants cultivated in coconuts fibers exhibited the highest plant growth (5.60 cm) as compared to the plants cultivated in sandy soil (4.12 cm); however, the conditioning effect was limited in this case. Also, in this experiment, the amount of hydrogel used only affected the plant roots size. Additional analyses showed that the plant growth process is enhanced in clay soil as compared to sandy soil. Here, a synergistic beneficial effect was noticed between the type of soil and the amount of hydrogel used as conditioners. A small amount of hydrogel (≤ 0.75 wt%) had an apparent positive effect on the plants' growth process when they are cultivated in clay soils. In summary, the results presented here allow inferring that these composite hydrogels can be ranked as promising materials for use as soil conditioners.