Objective To improve the ecological environment and sustainable development status of vegetation in the Hutuo River Basin, this study investigates the poor soil structure and weak water and nutrient retention capacity of sandy soil in the Hutuo River of Shijiazhuang city.

Methods Through simulated experiments, five different soil water-retaining agents (attapulgite-sodium polyacrylate water-retaining agent, biochar-bentonite water-retaining agent, humic acid-type water-retaining agent, polyacrylate water-retaining agent, and starch-based SAP) were selected as research subjects to explore their improvement effects on sandy soil. Furthermore, through an orthogonal experiment, different proportions of water-retaining agent, corn straw, and biochar were added to the soil to investigate the water- and nutrient-retention effects of soil under different substrate ratios.

Results When the dosage of the water-retaining agent was 1.0%, except for the humic acid-type and polyacrylate water-retaining agents, the soil moisture content of the other water-retaining agents was > 85%, and soil electrical conductivity was > 1 500 μS/cm. However, soil compaction occurred when 0.1%–1.0% of the humic acid-type water-retaining agent and 0.5%–1.0% of the starch-based SAP water-retaining agent were applied. Therefore, the attapulgite-sodium polyacrylate water-retaining agent was more suitable for the sandy soil in this region and exhibited better water retention performance. The effects of the three factors—water-retaining agent, corn straw, and biochar—on substrate soil moisture were ranked in descending order as follows: water-retaining agent > corn straw > biochar. The order of influence on substrate soil electrical conductivity was as follows: water-retaining agent > biochar > corn straw. The effect of the water-retaining agent was significant. With increasing water-retaining agent dosage, soil moisture and electrical conductivity were significantly higher than those of the control group. However, with the addition of corn straw, its effects on soil moisture content and electrical conductivity gradually decreased. When the water-retaining agent was 10 g, corn straw was 0 g, and biochar was 20 g, the soil exhibited the best water retention performance.

Conclusions The attapulgite-sodium polyacrylate water-retaining agent exhibits the best performance. The optimal formulation for substrate water retention performance is 10 g of water-retaining agent, 0 g of corn straw, and 20 g of biochar per kg of substrate, which is suitable for ecological restoration and plant growth in the sandy soil of the Hutuo River Basin.