Recurring droughts in South Africa's dryland rangelands have profound effects on ecosystem health. Consequently, identifying sustainable soil moisture content techniques is critical for enhancing plant growth to support ecosystem function. Soil moisture content was measured daily for five weeks using the field capacity as a reference and compared within the two mulching densities, high and low versus bare soil. The effect thereof was evaluated on growth parameters: emergence, relative growth, and survival rate of three subtropical grasses (Cenchrus ciliaris, Chloris gayan, and Panicum maximum) in seedling trays under a greenhouse. Soil moisture content significantly differed in all the treatments (p < 0.05); the mulching treatments retained half their moisture compared to the no cover treatment, which lost more than 77% moisture. The evapotranspiration was cumulatively lowest in the high-density mulching. Overall, Chloris gayana and Panicum maximum had the highest emergence (> 40%) and relative growth in the mulching treatments, while Cenchrus ciliaris emerged better (56%) and had relative growth in the no cover. By Week 6, many seedlings did not survive; however, Panicum maximum persisted in the high-density mulching with almost 17% seedlings survival. The mulching effect improved soil moisture content, thus providing more conducive conditions for germination and survival, especially of understorey grasses. While this approach is effective for certain grass species, it has demonstrated ecologically significant enhancement for soil moisture content and reducing evaporation, potentially promoting good soil structure and health.