Assessment of bio-based hydrogel as an alternative growth medium for seed germination and seedling growth in urban farming

Sustainable agriculture aims to meet the needs of the people in the present as well as in the future. The inadequate supply of vegetables raises dependency on imports for the growing population. To reduce import dependency, effective approaches in urban farming are emerging. One of the approaches is the application of hydrogel as a growth substrate in urban farming. This comparative study focuses on the characterisation of cellulose-based hydrogel sourced from cotton and its application as a seed germination medium in comparison to soil and perlite. Hydrogel is prepared by using cotton linter, sodium hydroxide, urea and epichlorohydrin as the cross-linker. Analyses to characterize soil, perlite and hydrogel (cryogel) were performed through gel fraction, field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). Seedling growth performance for four plant species ( Ipomoea aquatica , Brassica juncea , Lactuca sativa , Solanum lycopersicum ) was recorded after 15 days on each growth medium. Hydrogel crosslinking strength was at 92.49% based on the gel fraction analysis and the swelling of the hydrogel reached 65.00% in ten days. The FESEM analysis shows the hydrogel has a porous structure. Growth of Ipomoea aquatica in hydrogel medium was better than in soil. Hydrogel medium has room for further improvement through future research and development in urban farming. Graphical abstract