Soil health is something we hear a lot about these days. Cover crops, soil health tests, diversity in crop rotations and reduced compaction are all ways to improve soil health. However, there is some low-hanging fruit that farmers may be missing.
Minimizing soil erosion from water is a way to improve soil health that does not require a large investment in equipment, time and seed. Water erosion damages soil health in two ways. First and most obvious is by thinning the A horizon, or topsoil, and exposing the less productive subsoil. Second, and possibly the most destructive, is by raindrop impact and running water sorting soil components and degrading the soil by leaving behind less productive components.
Water soil erosion
Water erosion is a multiple-step process that starts with rain impacting bare soil. Raindrops hit with the force of a small bomb exploding, and such force can destroy soil structure at the surface. Soil is thrown into the air, and when the soil particles fall back to earth, the particles are suspended in water. Sand, silt, clay and organic matter are separated from one another in the moving water.
The heavier sand settles out of the soil water solution sooner than the lighter clay and organic matter. As silt particles settle out, they fill pores at the soil surface and form a crust, reducing the ability of the soil to absorb water.
Clay and organic matter are the lightest weight of the soil particles and are carried the farthest, often leaving the field and entering surface water. Clay and organic matter have a negative charge associated with them, and the negative charge holds soil nutrients for plants to use for growth and development. Loss of clay and organic matter reduces the ability of the soil to supply nutrients to plants.
Even small changes in the percentage of sand, silt, clay and organic matter can impact soil productivity. Sand settling out on the field can bury more productive soils and reduce crop productivity.
Crop residue left on the soil surface acts as a cushion against raindrop splash. Think of crop residue as an airbag for your soil. An airbag will keep you from impacting your vehicle’s steering wheel or dashboard in an accident. Crop residue will keep the raindrop bomb from exploding on the surface of bare soil.
Management of crop residue that leaves the soil surface covered is one of the best ways to improve soil health, whether or not you use cover crops. Tillage that buries residue reduces the impact of cover crops and slows or eliminates any soil health improvement you are trying to accomplish by planting cover crops. Reducing erosion is the first step to improving soil health.
Okonek is the Extension agriculture agent in Trempealeau County, Wis.