Soil erosion may be caused by wind, or more water. Water run-off down a slope washes away topsoil, leaving the soil on the slope with fewer nutrients and carrying sediment into nearby bodies of water. Increasing the total amount of plant cover on a slope and adding organic matter to the soil are two ways to decrease soil erosion. These methods work best on slopes with less than a 50 percent slope.
How Plants Decrease Erosion
Plants control erosion in 2 ways: by holding soil in place and by accelerating raindrops before they hit the soil. Perennial plants which develop deep permanent root processes help bind soil together and slow down water as it runs off the slope. Plant leaves and stems shelter the soil from direct rain, so hard raindrops are much less likely to dislodge soil. For year-round gains from leaf cover, choose plants.
Plants for Erosion Control
For full sun locations, try “Baby Tears” stonecrop (Sedum record chloroticum “Baby Tears”) and “Blue Chip” juniper (Juniperus horizontalis “Blue Chip”). This juniper is hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9, and Stonecrop is hardy in USDA zones 4 through 9. Aztec grass (Liriope muscari “Aztec Grass”) and Big Blue lilyturf (Liriope muscari “Big Blue”) work well in partial shade. Aztec grass is hardy in USDA zones 7 through 11 and lilyturf in USDA zones 5 through 11.
Holding Soil in Place
While plant origins do help hold soil in place, strong water run-off can pull soil from the roots. To protect against this, distribute compost or mulches 2 inches thick across the soil surface. Mulches are especially valuable for protecting soil while new plants are growing. In locations where planting isn’t an option, heavier mulches like crushed stone or wood chips could be a replacement. Crushed stone, however, won’t increase the amount of organic matter from the soil. When slopes are between 33 and 50 percent, jute netting or erosion control blankets may be asked to hold the dirt and soil set until the perennial plants form adult root systems and establish themselves. Use drip irrigation systems to water plants to maintain the soil in place on the slope.
Helping Soil Drain
Organic mulches, especially compost, have an additional advantage of adding organic matter to the soil as they decompose. Over time, this makes soil more porous, so more water may be absorbed into the soil rather than running off the slope. Soil high in organic matter also drains more quickly and grows healthier plants. Furthermore, compost buffers soil pH and gives plant enzymes, which in turn encourage lush growth and make plants a much more effective way of erosion control.