Dual Antifreeze and Sustained Release Cellulose Nanocrystal-Humic Acid Nanocomposite Hydrogel for Soilless Cultivation

Soilless cultivation relies on hydrogel matrices for water and nutrient management, but conventional hydrogels lose performance at low temperature and show unstable sustained release. Here this study develops an antifreeze sustained-release hydrogel (P-GTCH) that integrates l-proline (L-P) with a humic-acid-modified cellulose nanocrystal nanocomposite (CNCs-HA) for nanoenabled controlled release. L-P suppresses ice nucleation via hydrogen bonding, while CNCs-HA boosts HA loading and enables controlled transport within the cross-linked network. HA shows slow, continuous release governed by Fickian diffusion, achieving 96.7% cumulative release over 12 days at 0 °C and mitigating poor fertilizer release in cold environments. P-GTCH provides mechanical support for plant roots, and the synergistic effects of L-P and HA maintain lettuce germination above 86% at 0 °C while promoting root growth. This biobased, biodegradable platform is scalable for low-temperature soilless cultivation.