Development and Characterization of Lignin‐Based Hydrogel for Use in Agricultural Soils: Preliminary Evidence

In arid and semi‐arid regions of the world, agricultural production is greatly limited by water scarcity and inefficient water use. Water‐absorbent hydrogels are a technological solution that can retain soil water for plants. A lignin‐based hydrogel as a natural plant‐based water absorbent is prepared from lignin alkali polymers and poly(ethylene glycol) diglycidyl ether (PEGDGE) in adjusted alkali (NaOH) solution. The maximum swelling capacity of the hydrogel is achieved in 1.5 m NaOH with 0.5 mmol PEGDGE g. Water swelling capacity is 34 g g dry weight of hydrogel in distilled water, which is reduced to 53% and 64% in 0.1 m NaCl and 0.1 m CaCl 2 solution, respectively. Biodegradability and phytotoxicity tests show that 6.5% of the sample mass decomposed after 40 days of incubation in soil solution media and the hydrogel is not phytotoxic to wheat seeds. These findings support the use of the lignin‐based hydrogel as an environmentally friendly additive to promote water retention in dry, saline soils. Due to the limitations of this study, further assessments are needed in order to understand the efficiency of lignin‐based hydrogel application in different soils with different biota.