Hydrogels are gaining prominence in sustainable agriculture due to their water-retention capacity, biocompatibility, and tunable physicochemical behavior. Among natural polymers, alginate is particularly attractive because it forms hydrogels under mild conditions and provides a versatile platform for controlled release, soil conditioning, and environmental remediation. This review integrates advances in alginate-based hydrogel technologies from 2001 to 2024 through a combined bibliometric and patentometric analysis. A total of 266 scientific articles and 460 patent families were identified, revealing sustained growth in both research output and technological development. Encapsulation and controlled-release systems dominate the landscape, followed by soil and water treatment applications, while postharvest preservation, in vitro cultivation, and biodegradable packaging emerge as expanding areas. Overall, alginate-based hydrogels represent a multifunctional, biodegradable platform supporting precision agriculture and sustainable production systems within a circular bioeconomy framework.