Development and Characterization of Biobased Superabsorbent Materials for Agricultural Applications: Study in Lettuce ( Lactuca sativa L. ) under Drought Stress

The main objective of this research was to develop biobased superabsorbent materials (SAM) able to control humidity in soils. For this purpose, two abundant biopolymers (alginate and chitosan) were studied. Concentration of both polysaccharides, cross-linking time, CaCl 2 and acetic acid concentrations were evaluated through Taguchi design. Then, two formulations were selected and fully characterized. Samples were tested in soil substrate in two different concentrations to evaluate the effects in lettuce plants grown under hydric stress. Swelling degree significantly varied with the studied factors (822–8932%, after 24 h in distilled water). The two selected formulations had the minimum acetic acid and CaCl 2 concentrations, and cross-linking time tested, but the highest chitosan content, expecting an elicitor effect in the plants. The selected materials showed superabsorbent properties. Addition of 5% w/w of either biobased materials to soil substrates led to noticeably more vigorous specimens after 6 days of drought compared to lettuce grown in substrate without SAM. However, some phytotoxicity is suspected. Further assays are necessary to optimize chitosan content improving soil properties while stimulating plant growth without phytotoxicity. Overall, results showed that Chitosan-Alginate SAMs might be considered as promising sustainable agricultural devices.