What Is Soil Erosion and How Do You Stop It?
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What is soil erosion and how to stop it? Soil erosion is the loss of topsoil, the upper layer where most nutrients and organic matter are found, as water, wind or tillage moves it away. In a garden, the effect shows as thinner beds, exposed roots and runoff that carries fertility out of the growing area. This article explains the main ways erosion happens and the practices that slow it, using two Penn State Extension pages.
Quick answer
- Soil erosion is the movement of topsoil by water, wind or tillage, and bare soil is the most exposed to it.
- Cover crops protect the surface from raindrop impact, and their living roots hold the soil in place, according to Penn State Extension.
- Tillage can move soil downslope, and Penn State describes plowing on the contour and shallower passes as ways to reduce that movement.
- Crop residue and organic matter on the surface help soil absorb water, which lowers runoff and the loss that follows it.
What erosion removes
Topsoil is the layer that holds most of the organic matter and nutrients a plant uses. When it moves, the bed loses the material that supports growth, and the plants left behind may sit in subsoil that holds less water and fewer nutrients. The Penn State tillage page makes this point for fields, noting that the soil on eroded spots can have “lower infiltration rate, lower percolation and water holding capacity, and contains fewer plant nutrients.”
Erosion can be visible or slow. A heavy storm can move soil from a bare slope in one afternoon, while steady loss over many seasons can thin a bed without anyone noticing. The result is the same: less soil depth, less water held in the root zone and less fertility for the next crop.
Water, wind and tillage
Most garden erosion is caused by water or wind acting on soil that has no cover. Penn State’s cover crop page explains that the protective role of plants comes from how they meet the surface. Plants and their residue physically block raindrops from hitting bare soil directly. Without that cover, the impact of rain can loosen fine particles and send them into runoff.
Tillage is a separate cause, and it can move soil even when no rain falls. The Penn State tillage page defines the process this way: “Tillage erosion is the downslope movement of soil due to gravity.” Each pass with a tool can push soil down a slope, so the shoulders and upper parts of a slope lose soil while the lower parts gain it. This is why a garden on a slope can show thin soil at the top and piles of soil at the bottom.
Slope changes where the soil goes
The Penn State tillage page explains that “Tillage erosion is the worst on shoulders and upper side slopes, while it deposits soil at lower side slopes and foot slopes.” Water erosion works in a different place. The same page notes that water erosion is “typically greatest at the lower side slopes and foot slopes.” Together, the two processes can leave the upper slope thin and the lower slope overloaded with soil.
For a home gardener, the practical meaning is that a bed on a slope needs more attention at the top, where soil is most likely to thin, and at the bottom, where runoff gathers. The sources reviewed here describe the pattern for fields, and the same logic applies to a garden on a slope, but they do not give measured figures for garden-sized beds.
How the loss feeds itself
Erosion can make itself worse. The Penn State tillage page describes a chain: “The reduced productivity of the outcroppings also results in less soil cover and because less crop residue is returned to the soil the organic matter content becomes very low – further decreasing infiltration and increasing runoff.” In short, a thin spot grows fewer plants, returns less residue, holds less organic matter, takes in less water and sheds more of what falls on it.
This loop is the reason prevention matters more than repair. Once the topsoil is gone, rebuilding it takes time. The sources do not give a rate for rebuilding topsoil in a garden, but the mechanism shows why keeping the surface covered is the first step.
Cover crops as the first defence
Penn State Extension treats cover crops as a direct control for erosion. The cover crop page says that “Cover crops help prevent soil erosion by physically shielding the soil surface from raindrop impact, while living roots hold the soil and improve aggregate stability.” The shield limits the splash that loosens soil, and the roots bind the particles into stable clumps that water cannot carry away as easily.
The same source says that “A cover cropped field always reduces erosion compared to no cover crop, but some functional groups outperform others.” This means that any cover is better than bare soil, while the choice of species can change how much protection a bed receives. Roots that are deep and fibrous are described as useful for reducing erosion, which is one reason species choice matters.
Penn State also states that “Reducing erosion improves water quality and keeps high-value topsoil in place.” The benefit goes beyond the bed itself, because soil that stays in place does not carry nutrients into streams and runoff channels.
Managing the cover after it grows
A cover crop protects the soil only while it is in place, so the way it is ended matters. The Penn State cover crop page says that “Mowing tall cover crops before tillage can help manage residue, while mowing should not be done before roll-crimping.” The page treats roll-crimping and tillage as different ways of ending a cover, and tillage is the option that works the residue into the soil.
The page also notes that tillage helps residue break down faster, which can release nutrients sooner. That benefit has to be weighed against the loss of surface cover, and the choice depends on the bed, the crop that follows, and how much soil is at risk. For a garden bed, the simplest rule from these sources is to keep some residue or living cover on the surface as long as possible.
Gardeners who want to see how to layer organic material on the surface can read how to cardboard mulch. For the soil side of the same question, see how to keep garden soil healthy.
Reducing tillage and working the slope
The Penn State tillage page lists practical changes to tillage. It says growers can “manipulate tillage practices like plowing on the contour, using tools that drag less soil, cultivating more shallow and slower, and using fewer tillage passes.” Each change reduces the amount of soil moved downslope with every pass. Plowing on the contour follows the land’s shape rather than running straight up and down it, so the soil is less likely to slide.
In a garden, the same ideas translate into fewer digging passes, shallow work where possible, and rows or beds laid across a slope rather than down it. The sources reviewed here describe these ideas for fields, so a gardener should adjust them to the size and shape of the bed.
What we could not verify
The sources reviewed for this article do not give a rate of soil loss for home gardens, a number of years for topsoil to rebuild, or a measured reduction for specific mulches. The two Penn State pages focus on cover crops and field-scale tillage, and they do not address every garden method. The Oklahoma State and eXtension pages returned errors and were not used.
What the sources do not say
The sources do not say how much a gravel or plastic layer reduces erosion, how steep a slope must be before erosion becomes a serious problem, or which cover crop is best for a particular garden. Those questions need local trials or local extension advice.
How we chose
Sources were limited to non-retail pages from one university extension program. Both pages returned HTTP 200 and were opened on 2026-10-27. Quotes in this article were checked against the fetched text. Two other extension pages returned errors and were not used, and commercial pages from the search results were excluded.
Frequently asked questions
Is soil erosion only caused by rain?
No. The Penn State tillage page describes tillage erosion, which is the downslope movement of soil caused by tools and gravity. Water and wind also move soil, but tillage can move it even on a dry day.
Does a cover crop stop erosion completely?
The Penn State cover crop page says a cover-cropped field “always reduces erosion compared to no cover crop.” It does not say the loss stops entirely, and the amount of reduction depends on the species.
Why are the bottom of slopes often piled with soil?
The Penn State tillage page says tillage deposits soil at the lower side slopes and foot slopes, and water erosion is also typically greatest there. Soil that moves downhill collects at the bottom.
Should a gardener stop tilling altogether?
The sources do not recommend stopping tillage completely. They describe tillage changes such as shallower passes, fewer passes and contour work, which reduce soil movement while still allowing the bed to be prepared.
Why does erosion get worse over time?
The Penn State tillage page describes a loop in which thin soil grows less, returns less residue and holds less organic matter, which lowers infiltration and increases runoff. Each step makes the next loss more likely.
Sources
- Penn State Extension, “Cover Crop Species Selection,” https://extension.psu.edu/cover-crop-species-selection (opened 2026-10-27)
- Penn State Extension, “Tillage Erosion and Its Interaction with Water Erosion,” https://extension.psu.edu/tillage-erosion-and-its-interaction-with-water-erosion (opened 2026-10-27)
