It is time to get serious about soil erosion. Soil is the skin of the earth and yet we are peeling it off slowly as erosion continues above what is considered ‘tolerable’. Unfortunately, what we may think is tolerable may not be sustainable at all (but that will be the topic of a future article).
What we want to highlight today is that we have the tools to eliminate soil erosion – so let’s put them to work!
1. Combating interrill (sheet) erosion
Sheet erosion is a term we still use, but in reality, it is very rare to see erosion taking place in sheets. In the real world, erosion starts when raindrops impact the soil, where it disperses aggregates, followed by very shallow runoff carrying it to rills of concentrated flow.
Eliminating what is called interrill erosion is the first and most important wall of defense. The best thing farmers can do to eliminate interrill erosion is to keep soils covered with mulch or living vegetation.
Keeping soils covered breaks the kinetic energy of raindrops, protecting soil aggregates from disintegration and the soil from sealing up. The cover also helps slow down runoff so water has time to infiltrate. This cover is also called ‘armor’.
To achieve continuous cover, it is highly desirable to use no-tillage and plant cover crops to compensate for insufficient cover from residue. The organic residue is also the food source for soil organisms that, with the living roots of plants assist in improving soil aggregation and macro-porosity so water can infiltrate quickly into the soil.
Solid manure (or manure with solids) can be added as another way to improve soil organic matter and biological activity to improve soil aggregation and infiltration capacity.
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2. Combating rill erosion
Rill erosion is caused by concentrated flow when runoff forms rivulets carrying soil off the field. The practices to combat interrill erosion are essential to eliminate rill erosion. Beyond that, farmers can use strip cropping – the practice of planting alternating strips of high and low residue crops along the contour.
Properly managed, these strips ensure that there are always high residue strips covering at least part of the field. It can still be a helpful practice if farmers grow low-residue crops such as corn silage or soybeans. Contour planting is another important practice to eliminate rill erosion because it helps avoid runoff flowing along rows.
3. Combating gully formation
Where high volume flow from a large area concentrates, the danger of gully formation is great. This is where maintain permanent vegetation with dense root systems to slow down runoff and hold soil together can still be important. Maintenance of these grassed waterways is important.
First, the grass needs to be mown regularly to keep the vegetation short (3-4”). This causes water and any soil particles to enter further into the waterway and slows down the formation of bund at the edge of the waterway. Mowing also stimulates the grass to tiller, thus vegetating bare spots.
Nonetheless, a bund will form over time and this bund needs to be leveled from time to time. This may be a task to take on after small grain harvest this summer by disking the bund and leveling the edge of the grassed waterway.
When the edges are leveled and tilled, it is crucial that they be reseeded immediately. Another way of reducing gully erosion is to reduce concentrated flow entering a field. I often see water from a road or other impervious surface or water from a spring, starting the process of gully formation.
Talk to your Soil and Water Conservation District or USDA-NRCS Office for the best way to deal with this concentrated source of water and spread it out so it can infiltrate in your field without causing rills and gullies. All the practices work hand-in-hand and by using them together, you can eliminate erosion from your field, guaranteeing a productive resource for generations to come.
We have the tools – let’s put them to the task.