We investigated substrate material and the effects of different fertilizers and water levels as variable factors for slope restoration. A field rainfall monitoring experiment was carried out to explore morphological changes in Amorpha fruticosa L., the water-holding capacity of its leaves under different water and nutrient gradients, and the nutrient losses from the substrate. The results showed that nutrient loss by runoff was significantly affected by fertilizer use and they increased with the increased application of fertilizers. The concentration of nitrogen in runoff was insignificant, the concentration of phosphorus was increased, and the runoff concentration of potassium was decreased after increasing water-retaining agent levels in the substrate. The concentration of nutrients in runoff from rainfall generally followed a trend of slight fluctuations, then a rise, and finally a decrease. The addition of F2 fertilizer produced the lowest nitrogen losses from substrate material and reduced the leaf area where the addition of phosphate fertilizer had a significant effect on crown diameter. At greater content of the water-retaining agent, the water in substrate material increased, resulting in increased water absorption by the plants and increased relative water content of leaves. Ultimately, W3F4 was the most favorable combination of water-retaining agent and fertilizer concentration for plant growth, which may be related to runoff losses. This combination provides optimal conditions under which the plant can maintain a perfect balance of nutrients and thus improve plant growth indices.