Soil erosion isn’t just something that happens on hillsides. It's actually a naturally occurring process that can happen in any area, including your own garden.
Erosion is the removal or wearing away of topsoil. It often occurs when the ground is left bare with no plants of any sort holding the soil in place. Without plants, the soil erodes away. It can happen slowly over time or, in some cases, it can occur very quickly, such as when the area receives a heavy rainfall in a short amount of time. Here’s what causes erosion and how to prevent it in your garden.
Common Causes of Erosion
Generally, rain - especially excessive rain within a short period of time - can fragment soil aggregates. Once the soil is broken up, water pools on the ground’s surface beneath the loosened topsoil and causes it to wash away. How much soil erodes depends on several factors, including the nature of the soil and length and steepness of the area involved. For example, longer, steeper slopes tend to take more soil with them than shorter, more gradual slopes.
Large amounts of rain can cause streams to form, which may take with it the soil it encounters. Water often takes the path of least resistance and will charge through open areas, whether over the surface or under the surface, taking with it any soil, rocks, and debris in its path.
Wind is another common culprit, especially for lighter, more sand-like soils. Since the soil granules are so lightweight, they easily take flight, especially with strong winds. In fact, it was wind erosion or aeolian processes that led to the Dust Bowl in North America in the 1930s.
In nearly all cases of erosion, the soil is bare or nearly bare. By its nature, soil prefers to be covered with plants. The roots of plants, even weeds, keep soil in place. If you’ve removed large amounts of turf to plant a garden or expand your landscaping, you’ll want to take steps to prevent soil erosion until you’re ready to develop the site.
Bare soil isn’t the only trigger for soil erosion. Basically, anything that degrades the topsoil and compromises the soil structure can accelerate erosion. This includes soil with low organic matter, poor drainage, soil acidity and more. While they may not cause erosion directly, they do weaken the soil’s ability to stay put.
Additionally, if you have a large agricultural plot, tilling the soil may increase the incidence of erosion. When you plow, the direction you plow and even the depth of soil you plow all play a role in soil erosion. Instead, minimize your tilling or don't till at all to allow existing vegetation to cover the surface and prevent erosion.
How to Prevent Soil Erosion in the Garden
The ultimate goal is to protect your bare soil and avoid situations where runoff will occur. Bare soil wants to have plants on it! That’s why weeds tend to grow so quickly on bare soil.
Grow a Cover Crop
If you cleared the soil in the fall to grow a particular crop in the spring (or if you’d like to keep that spot clear all year, plant a cover crop in the interim. Cover crops do more than prevent soil erosion; they also increase organic matter, prevent weeds from taking over the garden, and add nutrients to the soil. Common cover crops including legumes, such as clover, vetch and peas, cereals and forage grasses. Another advantage? They’ll add more visual interest to the garden than just keeping the spot bare dirt. Once you’re ready to plant, just pull it up and the soil will be well-nourished and ready to grow the intended plants.
Plant Ground Cover
If you’re not sure what to plant, consider planting ground cover, or low-growing plants that add visual interest while keeping soil in its place. Examples including creeping phlox, lamb’s ear, dianthus, sedum, and thyme. All of these plants stay small in height and expand outward to quickly cover an area. They also tend to be water-wise and easy to care for, especially once established. Plus, they add color to your landscape and may attract beneficial insects.
Mulch does more than prevent weeds, it also prevents your soil from taking off. Spread two to three inches of wood chips, shredded bark, or straw over the bare area, remembering to add more when you notice it has thinned.
Manage Your Landscape
Whether you have a hillside or slope or you’re slowly working on a long-term landscaping project, it’s important to ensure your soil stays put. If you live on a slope, plant ground cover and use mulch or erosion control mats to keep soil in place. If your slope is super steep, get professional help to build a retaining wall or terrace the slope.
Soil compaction can also cause erosion. Consider aerating your grass in the spring and, if you have clay soil, consider aerating again later in the year. Also tend to your trees and shrubs to ensure they remain in good health. If you have soil pathways in your landscape, replace them with paved or pervious pavement to prevent soil runoff.