Agronomic evaluation of hydrogels containing antimicrobial agents applied on Lactuca sativa L. seeds and plantlets

Lettuce (Lactuca sativa L.) is a leafy vegetable commonly consumed in human diets. Greenhouse cultivation of lettuce often involves intensive agricultural practices, using compounds that negatively impact agroecosystems. In light of this, it would be useful to consider the potential drawbacks of using such compounds in lettuce cultivation. With the aim of replacing the traditional soil fumigation products, hydrogels containing slow-release biocidal compounds represent an innovative and sustainable solution. In this research, the ecotoxicological impact and agronomic performance of cross-linked hydrogels containing natural antimicrobial agents on lettuce seeds and plants were examined. For this purpose, six hydrogels, based on carboxymethyl cellulose (CMC) and alginate (AL) empty or loaded with aqueous microemulsions including ethyl isothiocyanate (Eth) or phenyl isothiocyanate (Phe), at different concentrations, were tested on seed germination and seedling growth. The influence of hydrogel treatments on lettuce growth parameters, including fresh weight, number of leaves, leaf surface, and susceptibility to moulds, was highlighted through seedling tests. In the present investigation we are able to report that during the detection time 72 h , significant differences were observed concerning parameters assessing the germination such the root elongation values and the percentage of germinated seeds (GI). Hydrogels containing combinations of CMC with Eth or Phe exhibited high levels of phytotoxicity (GI % = 26–42 %), indicating an inhibitory effect on seed germination and root elongation. Furthermore, a gradual dissipation of these inhibitory effects was observed over time. After 216 h all hydrogels demonstrated a phytotoxicity-free profile, with variable levels of biostimulant potential, particularly CMC with Eth and Phe (GI % = 105–112 %). Alginate hydrogels revealed encouraging results in promoting plant growth: however, hydrogels with Eth and Phe showed a decrease of fresh weight ranging from 5 to 10 % compared to AL itself. © 2025 The Authors.