Development and characterization of nanocellulose hydrogel for enhanced water retention and controlled nutrient release in sustainable agriculture

Abstract

This work presents the synthesis and characterization of a coconut shell waste-derived nanocellulose-based hydrogel for green agriculture. The hydrogel was designed to enhance water retention of soil and deliver controlled release of nutrients, addressing the major problems of drought and fertilizer inefficiency. Nanocellulose was prepared through acid hydrolysis after alkaline and bleaching treatment and cross-linked with citric acid to yield a urea-loaded hydrogel. Fourier Transform Infrared spectra verified the integrity of cellulose functional groups and the formation of new –COO⁻ bonds, evidencing good crosslinking and urea incorporation. X-ray diffractogram evidenced prominent crystalline peaks at 2θ ≈ 15° and 22.5°, signifying partial retention of cellulose I structure with reduced crystallinity, augmenting swelling and water-retention capacity. Scanning Electron Microscope images exhibited a sharp, porous, and networked structure that supports water uptake, nutrient transfer, and mechanical strength. Hydrogel exhibited a 50% increase in water retention and an 88% degree of nutrient release efficiency, greatly supporting soil parameters such as nitrogen level and water content. Soil analysis after treatment showed high ammoniacal nitrogen (7.6 mg/kg) and a notable rise in total Kjeldahl nitrogen (13.1%), confirming efficacy of nutrient delivery. These results set the hydrogel's dual function as a moisture regulator and slow-release fertilizer system. Overall, the nanocellulose hydrogel derived from coconut shells is an economically scaled, biodegradable, and environmentally friendly material for smart agriculture with benefits towards water conservation, reduced fertilizer loss, and climate-stressed crop productivity in a sustainable way.