Biodegradable cellulose-based hydrogel fertilizer with porous network for sustained NPK release and improved plant growth.

Excess nutrients from fertilizers can cause inefficient fertilizing, environmental pollution, and greenhouse gas emissions. Addressing this issue, this study developed a biodegradable carboxymethyl cellulose (CMC)/microfibrillated cellulose (MFC) hydrogel fertilizer using a biocompatible template, calcium carbonate nanoparticles, for effective nutrient release. The hydrogel fertilizer simultaneously encapsulated and controlled the release of nitrogen, phosphorus, and potassium (NPK). The resulting hydrogel attained water uptake of 20 g H2O/g dry hydrogel and retained more than 500 % of its weight in water after 10 days. More than 95 % of the hydrogel degraded within 60 days under soil burial. Uniform elemental mapping confirms homogeneous entrapment of nitrogen, phosphorus, and potassium. Release tests confirmed that it follows non-Fickian behavior that is well described by the Korsmeyer-Peppas model. In a 24-day pot trial with Allium tuberosum, 1 g of hydrogel dose delivered the greatest agronomic benefit. The tallest shoots (≈30 cm), longest roots (≈18 cm), and highest tissue water content were attained. The high dose of hydrogel of 3 g, highlighted the threshold beyond which osmotic imbalance can inhibit growth. This work introduces a scalable platform for synchronizing NPK delivery with crop demand, thereby minimizing fertilizer loss and supporting sustainable agriculture.