Potential of Cellulose-Based Superabsorbent Hydrogels as Water Reservoir in Agriculture

The present work deals with the development of a biodegradable superabsorbent hydrogel, based on cellulose derivatives, for the optimization of water resources in agriculture, horticulture and, more in general, for instilling a wiser and savvier approach to water consumption. The sorption capability of the proposed hydrogel was firstly assessed, with specific regard to two variables that might play a key role in the soil environment, that is, ionic strength and pH. Moreover, a preliminary evaluation of the hydrogel potential as water reservoir in agriculture was performed by using the hydrogel in experimental greenhouses, for the cultivation of tomatoes. The soil-water retention curve, in the presence of different hydrogel amounts, was also analysed. The preliminary results showed that the material allowed an efficient storage and sustained release of water to the soil and the plant roots. Although further investigations should be performed to completely characterize the interaction between the hydrogel and the soil, such findings suggest that the envisaged use of the hydrogel on a large scale might have a revolutionary impact on the optimization of water resources management in agriculture. 1. Introduction Superabsorbent hydrogels are a particular class of macromolecular gels, obtained by chemical stabilization of hydrophilic polymers in a three-dimensional network, in which the dispersed phase is water, present in substantial quantity. Currently, superabsorbent hydrogels are widely used as absorbent core for hygiene products (such as baby diapers), and this attractive business has motivated the interest of multinational companies toward the development of new technologies, with focus on both the “chemical definition” and the production processes of these materials [1–5]. However, most of the superabsorbents that are currently on the market are acrylate-based products; hence, they are not biodegradable and, most importantly, some concerns exist about their toxicity for use in agriculture or for any applications related to human consumption. As a result, the renewed attention of institutions and public opinion towards the Environment has led manufacturers of hydrogel-based products to consider the development of biodegradable superabsorbents [6–13]. Sannino and coworkers developed and patented a novel class of cellulose-based polyelectrolyte hydrogels, totally biodegradable and biocompatible, whose swelling capability can be modulated by adjusting several synthesis parameters [14–20]. Such hydrogels may thus absorb up to 1 litre of water or aqueous