Soil erosion is the displacement of the top layer of soil, a natural process often accelerated by human activity, particularly in agriculture. This upper layer, known as topsoil, holds the nutrients and organic matter plants need to thrive. The removal of this fertile material by wind or water severely decreases agricultural productivity and threatens food security worldwide. Preventing soil loss is paramount for preserving ecosystems, maintaining water quality, and ensuring the long-term sustainability of land use.
Protecting the Ground Surface
One of the most direct ways to combat soil erosion is to ensure the ground remains covered and undisturbed, shielding it from the immediate impact of weather forces. This surface protection is largely achieved through modern conservation tillage and the strategic use of additional vegetation. By minimizing or eliminating mechanical plowing, practices like reduced-till and no-till farming preserve the soil’s natural structure. This reduction in disturbance keeps soil aggregates intact, which enhances water infiltration and prevents the soil from being easily detached by wind or rain.
Cover crops provide a living shield for the soil, especially when the main cash crop is not growing. Species like cereal rye and clover are planted specifically for this purpose, not for harvest. Their dense root systems physically bind soil particles together, acting as a subsurface network that resists water flow and wind forces. Above ground, the foliage absorbs the energy from raindrops, preventing splash erosion and slowing the velocity of surface runoff.
Crop residue management involves leaving the remnants of the harvested crop (stubble) on the field surface. This stubble acts as a physical barrier that intercepts raindrops, preventing the detachment of soil particles. Maintaining just 30% of the soil surface covered with residue can reduce water erosion by at least 50% compared to a bare field. Furthermore, this layer of residue acts as a mulch, helping to conserve soil moisture by reducing evaporation and moderating soil temperature.
Managing Water Movement on Slopes
On sloped land, the momentum of flowing water is the primary erosive force, making it necessary to implement physical modifications that slow, divert, or capture runoff. Contour plowing involves tilling and planting perpendicular to the natural slope, following the land’s elevation contours. The furrows created by this method act like a series of small, horizontal dams that catch water as it runs downhill. This dramatically reduces the speed of the runoff, allowing more time for the water to soak into the soil instead of carrying away topsoil.
For steeper terrains, terracing breaks up long, continuous slopes into a series of shorter, more manageable sections. Bench terraces are constructed as level platforms, converting steep slopes into productive, flat steps. Broad-base terraces are earth embankments used on gentler slopes, primarily to safely remove excess water or retain it for infiltration. These structures shorten the distance water can flow uninterrupted, keeping runoff velocity below the threshold that causes scour erosion.
Engineered systems are used to safely channel excess water away from vulnerable areas. Diversion ditches are constructed near the top of a slope to intercept runoff before it gains momentum and flows across a field. This intercepted water is then directed toward a safe outlet, such as a grassed waterway. Grassed waterways are broad, shallow, vegetated channels designed to convey concentrated water flow at a non-erosive velocity, slowing the water and preventing the formation of erosive gullies.
Utilizing Field and Landscape Barriers
Vegetative barriers can filter runoff, stabilize boundaries, and reduce the erosive power of wind before it reaches crop fields. Windbreaks and shelterbelts are linear plantings of trees and shrubs established perpendicular to the prevailing wind direction. They reduce wind speed, which is a significant factor in soil detachment, especially in arid or semi-arid regions. A well-designed windbreak can offer protection to the soil surface for a distance up to 10 to 30 times the height of the tallest tree on the downwind side.
Vegetative buffer strips consist of permanent, dense vegetation, typically grass or a mix of trees and shrubs, planted along the edges of fields or next to waterways. These strips function as natural filters, slowing the speed of surface runoff and promoting the deposition of sediment and attached pollutants. The perennial roots stabilize the soil in these sensitive areas, and the dense plant material can trap 75% or more of the sediment carried in the runoff.
Strip cropping involves planting different crops in alternating, narrow strips across a field, often following the contour of the land. This technique alternates between erosion-resistant crops, such as hay or small grains, and erosion-susceptible row crops, like corn or soybeans. The dense, close-growing crops act as physical barriers that slow the flow of water and trap soil particles detached from the adjacent row crop strips. This systematic arrangement effectively reduces both wind and water erosion.