Stabilizing Loose Soil on a Hillside

Just 1 inch of topsoil takes 500 years to form, but wind and water can blow or wash away that inch -- and many more -- in seconds. Soil is one of the most important yet easily degraded natural resources on Earth. Hillsides are especially prone to soil erosion. If you have a steep area in your landscape, a few simple solutions can help stabilize the soil and prevent degradation and erosion.

Loose soil not only leads to erosion and run-off, but to slope destabilization as well. According to the University of Minnesota, slope stabilization methods change depending on factors such as slope grade, climate and soil type. However, most stabilization projects focus on increasing soil fertility or cohesiveness; strengthening the soil’s surface; or deflecting erosion-causing factors such as rain and wind.

Improving the soil’s fertility makes it less likely to blow or wash away. As an additional benefit, fertile soil creates better growing conditions for slope-stabilizing vegetation. Avoid using chemicals, which can contribute to harmful run-off, and amend the soil using natural materials. Organic choices include sphagnum peat, compost, decomposed manure, grass clippings, straw, sawdust and wood ash. Man-made amendments include sand, vermiculite, shredded tires, gravel or perlite. All increase the soil’s ability to retain moisture, nutrients and air.

One of the most effective -- and attractive -- ways to stabilize loose soil is through plants. Plants’ roots stabilize the soil from below, while vegetation above the ground prevents erosion. Drought-resistant plants with spreading, fibrous root systems work well. Whenever possible, choose species native to your region, as they require less irrigation and fertilizer, both of which contribute to harmful run-off. Native North American choices include groundcovers such as bunchberry, Canada anemone, sedge, violets, wild ginger and woods phlox. North American ornamental grasses include big and little bluestem, Indian grass, June grass, needle grass and switch grass. Trees and shrubs native to North America include black locust, pines, river birch and willows.

Restructuring a slope's surface also aids in soil stabilization. The practice of contouring or terracing reduces erosion by preventing water runoff. Agriculturalists and home landscapers alike can use this technique to stabilize soil on slopes with up to an 8 percent grade. Contouring takes advantage of the landscape’s natural shapes and drainage patterns; shape areas with less slope into terraces ranging from 3 to 12 feet wide. The ridges you create will slow or stop rain or irrigation water from flowing downhill -- and taking precious soil along with it. Contouring a hill can reduce annual average soil loss by about 50 percent, according to Purdue University.