Soil Quality Resource Concerns: Soil Erosion

USDA Natural Resources Conservation Service April 1996

What is erosion?

Wind or water erosion is the physical wearing of the

earth’s surface. Surface soil material is removed in

the process.

Why should we be concerned?

Erosion removes topsoil, reduces levels of soil organic

matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant

growth.

In soils that have restrictions to root growth, erosion

decreases rooting depth, which decreases the amount of

water, air, and nutrients available to plants.

Erosion removes surface soil, which often has the

highest biological activity and greatest amount of soil

organic matter. This causes a loss in nutrients and often

creates a less favorable environment for plant growth.

Nutrients removed by erosion are no longer available to

support plant growth onsite, but can accumulate in water

where such problems as algal blooms and lake eutrophication may occur.

Deposition of eroded materials can obstruct roadways

and fill drainage channels. Sediment can damage fish

habitat and degrade water quality in streams, rivers, and

lakes.

Blowing dust can affect human health and create public

safety hazards.

What are some signs of erosion?

Wind erosion:

- dust clouds,

- soil accumulation along fencelines or snowbanks,

- a drifted appearance of the soil surface.

Water erosion:

- small rills and channels on the soil surface,

- soil deposited at the base of slopes,

- sediment in streams, lakes, and reservoirs,

- pedestals of soil supporting pebbles and plant material.

Water erosion is most obvious on steep, convex landscape positions. However, erosion is not always readily

visible on cropland because farming operations may

cover up its signs. Loss of only 1/32 of an inch can

represent a 5 ton per acre soil loss.

Long-term soil erosion results in:

- persistent and large gullies,

- exposure of lighter colored subsoil at the surface,

- poorer plant growth.

How can soil erosion be measured?

Visual, physical, chemical, and biological indicators can

be used to estimate soil surface stability or loss.
- comparisons of aerial photographs taken over time,

- presence of moss and algae (crypotogams) crusts in

desert or arid soils,

- changes in soil horizon thickness,

- deposition of soil at field boundaries.

Physical indicators

- measurements of aggregate stability,

- increasing depth of channels and gullies.

Chemical indicators

- decreases in soil organic matter content,

- increases in calcium carbonate content at the surface,

provided greater content exists in subsurface layers,

- changes in cation-exchange capacity (CEC).

Biological indicators

- decreased microbial biomass,

- lower rate of respiration,

- slower decomposition of plant residues.

What causes the problem?

Water erosion

- lack of protection against raindrop impact,

- decreased aggregate stability,

- long and steep slopes,

- intense rainfall or irrigation events when plant or

residue cover is at a minimum,

- decreased infiltration by compaction or other means.

Mechanical erosion

- removal by harvest of root crops,

- tillage and cultivation practices that move soil

downslope.

Wind erosion

- exposed surface soil during critical periods of the year,

- occurrence of wind velocities that are sufficient to lift

individual soil particles,

- long, unsheltered, smooth soil surfaces.

(Prepared by the National Soil Survey Center in cooperation with the Soil Quality Institute, NRCS, USDA, and the National Soil

Tilth Laboratory, Agricultural Research Service, USDA)

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How can soil erosion be avoided?

Soil erosion can be avoided by:

- maintaining a protective cover on the soil,

- creating a barrier to the erosive agent,

- modifying the landscape to control runoff amounts and

rates.

Specific practices to avoid water erosion:

- growing forage crops in rotation or as permanent cover,

- growing winter cover crops

- interseeding,

- protecting the surface with crop residue,

- shortening the length and steepness of slopes,

- increasing water infiltration rates,

- improving aggregate stability.

Specific practices to avoid wind erosion:

- maintaining a cover of plants or residue,

- planting shelterbelts,

- stripcropping,

- increase surface roughness,

- cultivating on the contour,

- maintaining soil aggregates at a size less likely to be

carried by wind.