How Does Inorganic Mulch Help Water Retention?

Maintains Soil Porosity

• As rains strike the bare ground, the impacts slowly press soil particles into a compacted form. Compact soil hinders root spread and absorption processes -- the roots effectively suffocate from reduced air pockets and nutrient availability. Inorganic mulches, being permanent material on your topsoil, form a barrier to water impacts. For example, flat stone chips take the brunt of the rainfall's momentum as the soil below receives percolating moisture that preserves the friable texture. As a result, your soil retains water well without becoming compacted after each storm. Heavy inorganic mulch also withstands most winds so that your garden is protected even through heavy rainstorms.

Reduces Moisture Competition

• Properly placed mulch helps water retention by reducing moisture competition with invading weeds. For example, your new seedling transplants are trying to establish themselves in the garden. Inorganic mulch surrounding the transplants does not let light enter the soil below. Any weed seeds trying to germinate cannot access the light they need and fail to grow. Reducing weeds allows any moisture within the ground to exclusively supply your seedlings with ample water. Some organic mulches may shift over time, allowing weed seeds to germinate between the material and steal moisture from your desired plants.

Decreases Evaporation

• Soil is subjected to constant evaporation, especially in full sunlight locations. Inorganic mulches stop direct sunlight from striking the bare ground while reducing the overall evaporation of rain or irrigation moisture. Inorganic mulches, however, can heat the surrounding area, such as on hot and sunny days. To combat soil heating and possible plant damage, use a light-colored mulch to reflect the light back into the atmosphere. Your soil moisture remains within the ground while maintaining a mild temperature.

Runoff Barrier

• If you have a particularly strong storm, organic mulches tend to float away, especially if there is excessive runoff. Larger inorganic mulches, like stones, typically stay in place. With heavier mulch, your water runoff decreases dramatically. Your topsoil does not slough off into nearby drains, causing pipe clogs and reduced soil nutrient availability. Any water that travels below the mulch is easily retained for root uptake and vigorous garden growth.