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

Abstract

The main objective of this research was to develop biobased superabsorbent materials (SAM) ableto control humidity in soils. For this purpose, two abundant biopolymers (alginate and chitosan) were studied.Concentration of both polysaccharides, cross-linking time, CaCl2 and acetic acid concentrations wereevaluated through Taguchi design. Then, two formulations were selected and fully characterized. Sampleswere tested in soil substrate in two different concentrations to evaluate the effects in lettuce plants grownunder hydric stress. Swelling degree significantly varied with the studied factors (822–8932%, after 24 h indistilled water). The two selected formulations had the minimum acetic acid and CaCl2 concentrations, andcross-linking time tested, but the highest chitosan content, expecting an elicitor effect in the plants. Theselected materials showed superabsorbent properties. Addition of 5% w/w of either biobased materials to soilsubstrates led to noticeably more vigorous specimens after 6 days of drought compared to lettuce grown insubstrate without SAM. However, some phytotoxicity is suspected. Further assays are necessary to optimizechitosan content improving soil properties while stimulating plant growth without phytotoxicity. Overall,results showed that Chitosan-Alginate SAMs might be considered as promising sustainable agriculturaldevices.