Water scarcity in arid and semi-arid regions requires soil amendments that not only enhance moisture retention but are also biodegradable, locally sourced, and environmentally friendly. This study presents the development and evaluation of three biopolymeric hydrogel composites made from sodium alginate extracted from Sargassum spp., and functionally improved with frankincense (Boswellia sacra) extract and palm-derived biochar. A commercially available potassium polyacrylate hydrogel and research-grade acrylamide–acrylate copolymer were used as benchmarks for these natural formulations. A comprehensive evaluation of soil hydrogel interactions was conducted through RETC-modeled water retention curves, sequential drying-rewetting cycles, ImageJ crack morphology analysis, and post-treatment measurements of soil pH and electrical conductivity (EC). RETC modeling has shown that soil treatment increases saturated water content (θ) from 0.1170 (control) to 0.2679, with high pore uniformity (n = 4.05). On the contrary, COM remained only θs=0.1313 despite its high drainage index (n=5.0). R reached the highest θs=0.4795, but with low pore uniformity (n=1.63). Analysis of stenosis revealed soil treated with F. This represents 25% in COM and controls. Quantitative determination of the cracks indicates that COM developed 3.88-6.83% of surface cracks, where R was cracked , while the two soils F and F+B remained intact with 0% crack. Chemical analysis after two cycles of drying–rewetting showed that EC increased EC to 0.7 ds/m in COM, with F and F+B responsible for a threshold below salinity between 0.5 and 0.6 ds/m. The significance of matrix-specific hydrogel evaluation and the desorption stress dynamics specific to surface-applied superabsorbent are underscored by these results. This study provides a new path toward climate-resilient sustainable soil management systems in desert agriculture by managing the design of biodegradable polymers with capillary behavior and soil–water physics.