The use of mulches in landscape plantings provides other benefits as well. When water droplets land on bare soil, the impact causes soil particles to fly in all directions, resulting in soil crusting and slow water infiltration. Most mulches break the impact of the droplets, reducing soil erosion and crusting and increasing the penetration of water into the soil. In addition, mulches improve soil structure in several ways. As organic mulches decompose, they provide organic matter that prompts soil particles to aggregate.
Large aggregates increase aeration and improve moisture conditions in the soil.
These conditions, in turn, encourage additional root development and biological activity, further enhancing soil structure. Mulched soils are cultivated less frequently than bare soils. It is now known that soil structure is improved by not cultivating, but this relationship was not always understood. The theory was that the dust layer would obstruct the upward capillary movement of subsoil water and thus reduce soil water losses. Research over the past 40 years has shown that dust mulches conserve moisture in soils by inhibiting weed growth.