Ways to stop erosion where rain hits the ground
- Joe Christner: SWCD
- January 18, 2020
- 1553
Despite almost 100 years of soil-conservation efforts in our nation, soil erosion and soil loss by water are still the major sources of the decline of soil health, water quality and soil productivity. Concentrated efforts of USDA-NRCS, Soil and Water Conservation Districts, crop consultants, agribusinesses and Cooperative Extension in working with farmers have resulted in much progress to implement Best Management Practices to stop erosion in its tracks.
According to 2015 National Resource Inventory, average soil erosion by water on U.S. cropland decreased from 3.82 t/a/year (tons per acre per year) in 1982 to 2.71 t/a/year in 2015. That is a major achievement but still represents (together with wind erosion) almost 1 billion tons of soil lost from our nation’s croplands. It may be even worse than that because of the increased number of intense rain events we have experienced over the past few years. It gives another meaning to the expression, “When it rains, it pours.”
So what needs to be done? First, as much as possible, erosion needs to be stopped where the raindrop hits the ground.
This means stopping the first stage of erosion called interrill or sheet erosion. This level of erosion is basically invisible to the eye, making us think it is OK. Keeping soil covered at all times is the most important thing you can do to reduce sheet erosion.
This can be achieved by continuous no-till practices making sure enough crop residue is left to cover the soil. Leaving soil undisturbed also means it is less likely to be dislodged and run off. Cover crops will be needed for erosion control where insufficient residue is left after harvest of some crops like corn silage and soybeans. Controlling soil compaction is another important practice that will increase infiltration of rain and reduce runoff.
Sometimes there is still runoff that, when it concentrates in rivulets, can cause rill erosion. Rill erosion is where concentrated flow starts to eat away at soil surface due to scouring action of runoff. Rills are normally about 4 inches deep and normally do not interfere with field operations. However, when we see rills in the field, it is a sign that “T” (tolerable soil loss) has already exceeded, making it very important to avoid rills from forming.
The definition of “T” or tolerable soil loss is a level of erosion that will permit current production levels to be maintained economically and indefinitely. Conservation practices that can prevent or reduce rills are planting crops on the contour, contour strips with alternating crops, and narrow contour buffer strips to slow down water and filter out soil.
When rills grow to depths up to 18 inches, they are called “ephemeral gullies.” These gullies do interfere with field operations but can still be filled by tillage operations.
“Classical” gullies are deeper than 18 inches and need major repair work beyond tillage. If nothing is done to address them, they will grow even larger. Unfortunately we are seeing more gully erosion on our cropland. We need to better understand the conditions causing gullies so we can stop them from forming.
A practice that is often recommended for gullies is a grassed waterway. Farmers may be reluctant to use this practice because they take a portion of working farmland out of production, it must be protected from application of herbicide or tillage operations and it requires some degree of maintenance.
Protecting our croplands from erosion is still one of the most important things we can do to maintain productivity of our soils and the quality of our streams, and once you see rills, the tolerable soil loss is already exceeded, so urgent action is needed.
Would you like to know if your operation meets tolerable soil loss and what practices will reduce soil erosion on your farm? On-Field Ohio is a computer modeling tool that provides long-term average estimates of field scale erosion risk and soil loss and how voluntary changes in practices can reduce soil loss on your fields. Call Joe Christner at Holmes SWCD at 330-674-2811 for info.