Desert ecosystems, which occupy a substantial fraction of the global terrestrial surface, are predominantly composed of silica-rich sandy soils characterized by extremely low water retention capacity (<5 vol%), high hydraulic conductivity (>10⁻³ m·s⁻¹), rapid evaporative losses, and minimal structural cohesion. These intrinsic physicochemical limitations severely constrain sustainable agricultural productivity in arid and semi-arid environments. This study presents a quantitatively grounded, materials-engineered framework for transforming desert silica into a water-retentive and agriculturally functional medium through the synergistic integration of surface functionalization and hydrogel-assisted aggregation. Silica particles are chemically modified via organosilane grafting, increasing surface site density (Γ_mod/Γ_max ≈ 0.6–0.85) and reducing effective contact angle (θ: ~60–80° → ~20–35°), thereby enhancing wettability and adsorption capacity. Concurrently, incorporation of superabsorbent polymer (SAP) networks (0.5–2 wt%) introduces volumetric water absorption capacities exceeding 200–400 g·g⁻¹, enabling internal moisture storage and controlled release. A unified physicochemical model is developed linking surface energy modification, pore-scale capillary pressure (P_c ∝ 1/r), hydrogel swelling dynamics, and evaporation suppression mechanisms to the effective water retention function (θ_w). Model predictions, supported by pilot-scale simulations, demonstrate a 4–12× increase in available water content (Δθ ≈ 0.20–0.55), a 30–60% reduction in evaporative flux, and a significant shift in pore size distribution toward capillary-active regimes (r_eff reduced by ~2–5×). Aggregate formation further enhances structural stability, increasing resistance to erosion and improving root penetration pathways. Biophysical response simulations indicate that these coupled modifications can elevate seed germination rates from <10% to 65–85%, extend soil moisture residence time from 1–2 days to 7–15 days, and increase biomass productivity by a factor of 2–6 under controlled arid conditions. Importantly, the framework operates within established thermodynamic and soil-physics principles, avoiding non-physical assumptions and ensuring scalability. The proposed system provides a mechanistically consistent, energy-efficient, and scalable pathway for desert soil transformation, with strong implications for climate-resilient agriculture, water conservation, and sustainable land utilization in water-scarce regions. Please check the attachment for details