To meet the rising global food demand, agricultural production must increase by at least 70 % by 2050. The development of high efficiency water and nutrient retentive fertilizers is pivotal for enhancing crop yields in arid and semi-arid regions, serving as a crucial strategy for ecological conservation and sustainable development. Hydrogels, as porous polymeric materials capable of absorbing and retaining substantial amounts of water without dissolution, demonstrate exceptional water absorption and retention properties. These materials find extensive applications in combating desertification, agricultural production, and landscape greening. In this study, three reactive quaternary ammonium surfactants (CSP-L, CSP-O, and CSP-E) were successfully synthesized using chloromethyl styrene and amide-containing tertiary amines as precursors. Comprehensive investigations were conducted on their structural characteristics, surface activity, and their effects on hydrogel-modified soil water retention. Fourier transform infrared and nuclear magnetic resonance analyses confirmed the designed molecular structures of CSP-n compounds, with critical micelle concentration decreasing from 0.361 mmol/L for CSP-L to 0.0567 mmol/L for CSP-E as the hydrophobic alkyl chain length increased. Thermodynamic analysis revealed the micellization process to be spontaneous and exothermic (Delta G<0), with CSP-E exhibiting unique thermal stability enhancement upon heating. Furthermore, CSP-E was employed as a functional monomer to fabricate physically crosslinked hydrogels through hydrogen bonding, hydrophobic interactions, and chain entanglement. Investigations on the influence of CSP-E content demonstrated that increased incorporation led to denser hydrogel networks and significantly enhanced water retention capacity. The dehydration rate constant decreased from 0.01254 for CP(E)Gel-2-0.007 for CPEGel-5. In agricultural applications, soil amended with CPEGel-4 exhibited 33.14 % water retention after 30 days, representing a 294 % improvement over the control group (8.4 %), while simultaneously promoting chlorophyll synthesis by 37 % under semi-arid conditions. Mechanistic studies revealed that the hydrogels regulate soil pore structure and capillary forces to achieve controlled water release, providing an innovative strategy for efficient water resource utilization in arid agricultural regions.