Effects of sodium carboxymethyl cellulose on soil water retention and silage corn in the arid region of northwest China

China’s arid northwest region suffers from water resource scarcity, and the soil is mostly sandy with poor water retention capacity. Efforts to conserve water and to maintain soil moisture are crucial for agricultural production in this region. Therefore, this study explored the use of the natural polymer sodium carboxymethyl cellulose (CMC-Na), which poses no risk of environment, to improve soil hydraulic properties. The results showed that CMC-Na application increased the stability of water-stable aggregates (i.e., WR0.25) by 18.05% to 81.35%. Soil porosity increased to 8.75%-10.12%, with connected porosity ranging from 7.01% to 7.99%. Experimental treatment also altered soil pore shape, among which equant and elongated pores were the most abundant types (accounting for 89.88%-95.21%). Permanent wilting point (PWP) increased by 8.18%-38.95%, and mean available water capacity (MAWC) increased by 4.23%-21.05%. During the jointing, tasseling, and milk growth stages, soil moisture significantly increased concurrently with drip irrigation volume. W2 (2250 m³·ha⁻¹) and W3 (2700 m³·ha⁻¹) treatments showed increases of 5.64% and 10.17%, respectively, compared to W1 (1800 m³·ha⁻¹). Dry and fresh plant weight increased with increasing irrigation volume, and yield increased by 8.41%–10.96%. After applying CMC-Na, the W3 treatment group exhibited the most significant improvement in soil hydraulic properties, soil structure parameters, and crop growth parameters.