N-ZnO/MIL-125(Ti) Hybrid Filler-Reinforced Polysaccharide Hydrogel for Enhanced Water Retention, Nutrient Sustained Release, and Soil Fertility Improvement.

With increasing challenges of water scarcity and soil degradation in agricultural production, the development of efficient and sustainable soil conditioners has become increasingly important. To overcome the limitations of conventional hydrogel soil conditioners, including poor long-term water retention, uncontrolled nutrient release, and limited functionality, a multifunctional SA/SLS/XG-N-ZnO/MIL-125(Ti) composite hydrogel was synthesized using sodium alginate (SA), sodium lignosulfonate (SLS), and xanthan gum (XG) as organic matrices incorporated with nanozinc oxide (N-ZnO) and MIL-125(Ti). Characterizations by FTIR, XRD, and SEM confirmed the successful integration and uniform distribution of the hybrid fillers within the three-dimensional hydrogel network, resulting in enhanced structural stability and porous architecture. The composite hydrogel improved soil water-holding capacity to 77.67%, maintained 13.13% water retention after drying at 60 °C for 11 h, and exhibited stable water absorption during repeated cycles. Meanwhile, the hydrogel achieved efficient fulvic acid loading and sustained release, with cumulative release rates of 80.40%, 82.37%, and 88.67% under acidic, neutral, and alkaline conditions, respectively. In addition, less-visible colonization by Aspergillus niger was observed on the hydrogel under the tested conditions, and the hydrogel exhibited a degradation rate of 39.53% within 60 d. Pakchoi cultivation experiments further demonstrated its ability to promote plant growth. Overall, this multifunctional hydrogel integrates water retention, nutrient regulation, antibacterial activity, and biodegradability, providing a promising strategy for sustainable agricultural applications.