How Farmers Keep Topsoil From Running Off

Maintaining Crop Residue

• Reduced-tillage and zero-tillage farming methods reduce topsoil runoff by conserving crop residue. Reduced-tillage systems involve plowing less often and less aggressively than traditional methods. Zero-tillage systems use equipment like air seeders to eliminate tillage and use herbicides on fallow fields rather than tilling to kill weeds. Crop residue is left on the soil instead of being worked in. Stubble mulching is when crop stubble is spread out on the soil surface and tilled in a way that keeps residue on the surface. Residue keeps rainfall from touching the soil, so the water can’t move the soil.

Cover Crops

• Cover crops are close-growing crops that cover the soil, protecting if from runoff. On farms with widely spaced crops, like orchards, cover crops can be planted between rows to provide permanent protection. For other farms, careful planning of crop rotations to include cover crops helps reduce erosion. For example, farmers can include hay as a cover crop in rotation with cereal crops. Cover crops can also be planted after the main crop has been harvested, providing protection over the winter.

Vegetation

• Vegetation traps soil and slows the flow of water. Permanent strips of grasses or shrubs across a slope, known as strip farming, help stop runoff by interrupting the flow of water. Establishing grassed waterways where water naturally runs off or is directed to run off will hold soil in place and prevent the development of gullies.

Contour Farming

• Contour farming is when farmers till and seed perpendicularly to the slope of a hill. The small furrows left by these activities run across the slope, so they trap soil and slow the flow of water, reducing runoff. In contrast, farming parallel to the slope creates channels for water to run all the way to the bottom of the slope unchecked, increasing erosion. The steeper a slope is, the less effective contour farming is, to the point where it may actually increase runoff by concentrating the flow of water on very steep slopes.

Terracing

• Terracing breaks up the slope of a hill. Terraces are cut into the slope, creating tiers and shortening the length of the slope between flat areas. Shortening the length of the slope decreases the speed of the water, which greatly reduces the amount of topsoil that runs off. Water is directed to a safe area for it to run off.