Soil Erosion and Clear Streamwater

Water is the most precious resource in the Delta. Soil is vital, but many places in the U.S. and the world have fertile soils. What many western states lack is water, but most of Arkansas is blessed with abundant water. In certain areas, though, water that is available doesn’t meet current commercial, irrigation, recreation or drinking requirements. High quality water will become increasingly costly and valuable as we continue to grow cotton, soybeans, rice and corn in Arkansas.

According to the Arkansas Department of Pollution Control and Ecology, agriculture has impacted the quality of 2,597 miles of Arkansas streams. Sediment loading is the main reason that these streams are labeled "impacted." Fine soil particles eroded from the topsoil or stream bank are carried by the water, either limiting its uses or increasing the cost of using or treating it. Table 1 (page 2) identifies the watersheds of specific concern.

"Areas where a loose, shallow topsoil lays over a tight subsoil are the most susceptible to sheet erosion. Areas like the Arkansas prairie soils are dependent on a very fragile surface that could become unproductive if topsoil is not conserved."

Sediment causes more problems by silting in streambeds, which can modify aquatic habitat, retard runoff, and, at times, cause flooding. But the primary loss is to the land owner and tenant who need productive topsoil to maintain peak crop production.

Streams next to crop land carry soil particles broken from the soil surface by overland water flow. Splashing raindrops often begin the soil erosion due to the force of droplets striking the soil surface.

Sediment is the very best topsoil lost from crop land. The soil washed out of field drains and gullies and the erosion from stream beds and stream banks is usually more fertile than the subsoil that resists erosion.

Measures to reduce erosion and enhance production need to be implemented immediately if good conservation practices are not already in place. Reducing erosion keeps the nitrogen, phosphorous, potash, organic matter and other soil-borne nutrients in fields where they are sorely needed. Retaining more soil nutrition, organic matter and topsoil enhances the current crop and the long-term productivity of a field.

Table 1. List of streams in crop land areas that have been identified as impacted by soil sediment.
WATERSHED	COUNTIES
St. Francis River	Clay, Craighead, Cross, Greene, Lee, Poinsett, St. Francis
Blackfish Bayou	Crittenden, St. Francis
Village Creek	Craighead, Greene, Jackson, Lawrence
Brush Creek	Cross, Poinsett
L’ Anguille River	Craighead, Cross, Poinsett, St. Francis
Strawberry River	Independence, Lawrence, Sharp
Frenchmans Bayou	Crittenden, St. Francis
Eleven Point River	Randolph
Spring River	Randolph
Overflow Creek	White
Fourche La Fave River	Perry
S. Fourche La Fave River	Perry
Wattensaw Bayou	Lonoke, Prairie
Cache River	Clay, Greene, Jackson, Lawrence, Monroe, Woodruff
Bayou De View	Craighead, Cross, Jackson, Poinsett, Woodruff
Wabbaseka Bayou	Arkansas
Bayou Meto	Arkansas, Lonoke
Bayou Two Prairie	Lonoke
Big Creek	Crittenden
Fifteen Mile Bayou	Crittenden, St. Francis
Pemiscot Bayou	Mississippi
Tyronza River	Crittenden, Mississippi, Poinsett
First Creek	Cross, St. Francis
Second Creek	Cross, St. Francis
Big Boy Creek	Craighead
Eighteen Mile Ditch	Craighead, Greene
Larkin Creek	Lee
Little River	Mississippi, Poinsett
Whitner’s Creek	Craighead, Poinsett
La Grue Bayou	Arkansas
Deep Bayou	Jefferson, Lincoln
Bayou Bartholomew	Ashley, Drew, Jefferson, Lincoln
Boggy Bayou	Desha
Big Bayou	Chicot
Clay Ditch	Desha
Choctaw Bayou	Desha, Lincoln
Cypress Creek	Desha, Lincoln
Oak Log Bayou	Desha
Macon Bayou	Chicot, Desha
Red Fork Creek	Desha
Boeuf River	Chicot, Desha, Lincoln
Ditch Bayou	Desha

For most crop land in the river-bottoms and Delta, maintaining soil vegetative cover is the most effective way to prevent erosion and reduce stream turbidity (muddy water). Crop residue and plant foliage protect soil particles from the impact of falling rain drops that have enough force to dislodge soil. No-tillage, mulch tillage, reduced tillage and ridge tillage all reduce the amount of sediment leaving the field. Possibilities exist for tillage at times of low intensity rains rather than during peak rain intensities to reduce erosion.

Maintaining vegetative cover, such as no-tilling soybeans into wheat stubble, is probably the most effective way of preventing soil erosion.

Most erosion-related studies have been done on soils with slopes greater than 3 percent. However, sediment was measured leaving a fairly typical Delta cotton field near Clarksdale, Mississippi, that was graded to 0.2 feet of fall per 100 feet (0.2 percent) down the row. Runoff water and sediment from unrestricted field outlets were surprisingly high for these relatively flat fields (Table 2). The eroded soil particles in this experiment consisted of 76 percent clay and 19 percent fine silt and contained about twice the nutrients as the soil remaining in the field. Peak erosion was during storms soon after tillage. Fall disking, bedding and cultivation indirectly caused significant soil losses. Other work has confirmed that erosion is not limited to steeper slopes or areas that have been classified highly erodible (HEL).

Growers’ efforts to limit runoff from their farm can be very effective in reducing the sediment load in streams. The choice of crop production practices, the amount of cover retained on the soil, and maintaining vegetation in noncrop areas, such as grassed waterways where runoff concentrates, are all vital for retaining topsoil. Avoiding overgrazing on streambanks and steep slopes and maintaining grassed buffers along ditches and streams help prevent erosion from noncrop areas.

Using management practices such as irrigation scheduling, proper land forming and soil testing to guide soil nutrition all help conserve soil. This, in turn, reduces the sediment in runoff water reaching the streams, bayous and lakes.

Soil erosion is caused by the action of raindrops on soil. The force of large raindrops or intense rains dislodges soil particles. Clay particles are much less likely to dislodge from the soil surface than sand. However, clay particles are readily transported off a tilled field. Suspended soil particles add color to the runoff water in many areas of Arkansas. Any practice that enhances crop foliage or reduces plant skips in fields where the soil is loose provides protection from the impact of raindrops.

"Large drops may increase the sediment load in runoff 12 times more than a light rain."

Sheet erosion occurs when soil begins moving with the water. Sheet erosion isn’t noticeable from looking at water ponding on the soil or from investigating the field after a rainfall.

Rainfall may cause soil "packing" on freshly prepared seedbeds. Soil particles tend to seal the soil pores and reduce the surface infiltration rate. When this happens, only a small part of the rain soaks in and the rest runs off the field. If this happens when crops are growing rapidly, they may need more moisture within 3 to 4 days after this rain. Irrigation water may also run off the field under this condition, requiring another irrigation soon to avoid crop stress, thus increasing the cost of production.

The rate at which water is transmitted through the soil surface layer is highly dependent on the surface condition. For example, fine soil may seal the surface (especially after tillage) and reduce infiltration rates even when the underlying soils are highly permeable. This aspect is critical in silt loams, clays and clay loams and may be a factor that reduces moisture storage in silt loams (see Table 3). Under adverse conditions, three to four days may be required for a 1-inch rainfall to percolate through a tight, noncracking clay surface layer.

Woods and permanent grass sod areas absorb a greater amount of rainfall than other land uses. The infiltration is proportionately less based on the cropping practices (see Table 4).

Where sheet erosion progresses across a field, water concentrates in tiny rivulets causing the formation of small, well-defined channels called rills. This can occur on most soils, not just those classified as highly erodible.

"Erodibility of a soil depends on the physical properties of the soil, the steepness of the slope, the length of the slope (row) and the cropping practice. Cropping practice changes are one of the most important considerations for soil conservation because INTENSE RAINS WILL FALL, sooner or later."

For example, rill erosion can often be seen on the steep side of bedded rows raised above the level of the soil surface in the middles. Soil that erodes from the bed may only move into the row middle and accumulate there. However, it may advance beyond the rill stage at the lower end of the rows, resulting in soil loss from the field.

Gullies aren’t common on poorly-drained flat soils, but that doesn’t mean they don’t erode. Gully erosion is evident in every crop area of the state. The concentration of water produces gullies larger than rill erosion. These gullies aren’t wiped out with normal tillage. Farming gullies is costly and dangerous. They can cause damage to field equipment. In some cases they have caused tractor operator injury and accidental death. They may begin from "dead" plow furrows or water concentrating at the outlets of several drain furrows or tractor tracks. This natural pattern of erosion development will continue unless preventative measures are taken before rill erosion is established and gullies begin forming.

Soil conservation practices alone will not eliminate "coffee-colored" water in certain streams. Some soil particles are so small, or colloidal, that they remain suspended in water. This causes "cloudy" water anytime stream flow occurs. This may come from streambank erosion, wildlife activities, farming practices, forest or county roads, turnrows or construction sites. Sediment reaching streams and bayous is also being addressed by forest managers, road supervisors and construction site contractors. All enterprises can reduce sediment-laden runoff, which is called nonpoint pollution, when it reaches an open body of water.

Review your field layout and crop production practices. Consider implementing several conservation measures below that contribute to long-term soil productivity:

• Use no-tillage practices for fields where they have potential to make corn, cotton, rice, soybeans or wheat more productive.

• Use mulch tillage or reduced tillage practices to limit soil exposure to potentially erosive rains.

• Plant wheat on soils where drainage is satisfactory for obtaining a good wheat stand to protect soil from erosive winter rainfall. (See Fact Sheet 1012 – Drainage for Wheat Production.)

• Spread chaff and straw with the combine and leave this surface residue undisturbed. Use herbicides to kill the vegetation and get a well-designed no-tillage drill to seed through the dead vegetation and straw.

This gully is an example of the last, or most advanced, stage of soil erosion.

• Maintain flood on fields after harvest to protect soil from the impact of falling rain.

• Roll rice straw down in the fall and avoid tillage that incorporates all of the straw. Reduced and no-tillage experiments are underway to use the 3 to 5 tons per acre of rice straw after harvest. Rice produces more residue than most Arkansas crops and provides one of the most effective deterrents to soil erosion.

• Shift tillage operations from the spring period of intense rainfall to a time when the probability of intense rainfall is reduced.

• Use strip cropping to maintain shorter slope intervals and obtain some soil cover when other parts of the field need to be tilled. (An excellent application of this is seeding wheat and leaving standing strips of wheat to protect cotton during late April and May from sand-blow damage.)

• Plant winter cover (green manure) crops or allow winter vegetation to protect soil from erosion during the noncrop season..

• Follow precision land-forming guidelines for conserving soil as well as providing additional irrigation for grain and cotton crops. (See your NRCS district conservationist for criteria.)

• Use irrigation scheduling and tail water management to conserve water. Less water is less erosion!

Avoid burning rice straw (or wheat straw) unless there isn’t another alternative. The straw reduces erosion, improves the soil tilth, enhances moisture movement into the soil profile and provides organic material in soils.

• Install or expand buffers between field drainage outlets and ditches to prevent water from washing sediment directly into ditches. These ditches need regular cleaning because soil accumulates rapidly when buffers are inadequate to filter out sediment. For drainage areas of less than 80 acres (on 0 to 1 percent slope), a grassed "turnrow" about 25 feet wide removes almost all of the sediment.

• Maintain grassed waterways and try to prevent herbicide damage to the grass species.

• Install pipe drop inlets where rapid elevation changes cause water to drop more than a foot. This breaks up the energy of falling water and eliminates gullies. Properly installed inlets restore almost all the gully back into useful crop production.

• Build irrigation pits and reservoirs to catch and reuse runoff water. Siltation in these containment structures eventually reduces water storage capacity, but the silt can be dredged and applied onto fields.

• Use the natural short slopes or differences in elevation to separate fields by building permanent turnrows around fields for better access and erosion control. Permanent grass on the slope dropping to the field at the lower elevation resists erosion if runoff isn’t concentrated. Where water concentrates, consider a pipe drop inlet to break up the water energy without causing a gully.

• Install underground irrigation pipe and/or use surface irrigation pipe and tubing to replace ditches and canals. This avoids bank erosion and makes more efficient use of water by eliminating water evaporation and seepage losses.

• Stabilize streambanks with riprap or revetments (plant adapted tree species or install similar practices) to reduce streambank scouring, or in some cases, stream bed sediment load.

• Where natural wetlands occur, they filter soil from the water flowing through the wetland. The soil is difficult, if not impossible, to reclaim, so other practices are important to reduce the sediment load entering the wetland.

• Other inventive measures have been done by producers to time their tillage, minimize the flow length down a slope, or reuse water to avoid releasing sediment into ditches and streams. There are also many ways to control both erosion and sediment levels in streams that are effective.

Soybeans produce less crop residue than any other crop. Soybean cropping practices should, therefore, be managed most carefully to retain the topsoil. One or two tillage operations bury almost all of the soybean crop residue. No-tillage systems do the best job, by far, of protecting the topsoil. As an example, Table 5 shows data taken on Providence silt loam on a 5 percent slope near Holly Springs, Mississippi.

Erosion from no-tillage practices was less than 5 percent of that from comparable conventionally-tilled plots evaluated on 5 percent slopes. Similar erosion occurs on certain silt loam fields in Arkansas.

Table 5. Soybean yield, soil residue cover and soil erosion based on averages from crop practices in place for at least 3 years.
	Residue After Soybean Harvest* T/A	Crop Yield bu/A	Soil Loss T/A
Conventional tillage	1.9	19.3	8.7
Reduced tillage	2.2	21.7	3.6
No tillage	4.3	28.2	.3
Double cropped	3.9	---	1.2
Soybeans		26.2
Wheat		33.6
*Includes residue accumulated from previous years.

It is especially important to manage erosion on the thin upland soils and prairie soils with shallow topsoils. Many subsoils don’t provide the moisture storage or fertility needed for economical production.

Investigate the options available. Successful soil management practices offer advantages without unacceptable disadvantages. The better drained soils are the best candidates for no-tillage. Mulch cover deters erosion on silt loam soils. Contact your local county extension agent or district soil conservationist to explore measures to conserve your soil. Conserving soil may enhance your income. However, the impacts of conservation practices are more pronounced over the decades. Leave a legacy of fertile topsoil for your children and grandchildren.

In 1937, Franklin D. Roosevelt stated that, "A nation that destroys its soils destroys itself." The effect of centuries of poor cropping practices are apparent in India and countries of the Middle East and Africa. New weed control herbicides, no-tillage drills and other technology are now readily available. The time has passed for following the crop production principles of Cato the Elder (234-149 BC). He wrote, "The first principle of good crop husbandry is to plow well. The second principle is to plow again."

Murphree, C. L. and C. K. Mutchler. 1981. Sediment Yield from a Flatland Watershed. Transactions of ASAE. 24: 966-969.

Mutchler, C. K. and J. D. Greer. 1984. Reduced Tillage for Soybeans. Transactions of ASAE 27: 1364-1369.

1996 Water Quality Inventory Report, Arkansas Department of Pollution Control and Ecology, Little Rock, Arkansas.

USDA Natural Resource Conservation Service, Field Office. Technical Guide, Section III, Conservation Systems.

Viessman, W., J. W. Knapp, G. L. Lewis and T. C. Harbaugh. 1977. Introduction to Hydrology. Harper and Row, Publishers, New York, New York.

Special thanks to Larry G. Stauber, Crittenden County Extension agent - agriculture; Guy Dickey and Bob Morgan, Arkansas Soil and Water Conservation Commission; Jim Wise, ecologist, Water Division, Arkansas Department of Pollution Control and Ecology; Dr. Thomas A. Costello, associate professor, Soil/Water Engineering; and Dr. Carl L. Griffis, professor, BioSystems Engineering, for their assistance in the development of this fact sheet. This publication is part of an EPA 319(h) Water Quality project. The Environmental Protection Agency provided federal funds administered by the Arkansas Soil and Water Conservation Commission to the Cooperative Extension Service, University of Arkansas.

Gary Huitink, Extension Agricultural Engineer
Phil Tacker, Extension Agricultural Engineer
Jenny Sills, Extension Associate - Engineering
Dr. Mike Daniels, Extension Environmental Management Specialist - Agriculture
Jack C. Boles, Jr., Extension Agent - Agriculture, Newton County

GARY HUITINK is an Extension agricultural engineer, PHIL TACKER is an Extension agricultural engineer, JENNY SILLS is an Extension associate - engineering, and DR. MIKE DANIELS is an Extension environmental management specialist - agriculture, Cooperative Extension Service, University of Arkansas, Little Rock. JACK C. BOLES, JR. is an Extension agent - agriculture, Newton County.

Pictures of chickens, flowers, wheat, a boy looking through a magnifying glass, irrigation pipe, soybean pods, and fruits and vegetables.	Cooperative Extension Service





Cooperative Extension Service	Agricultural Experiment Station
Search \| Publications \| Jobs \| Personnel Directory \| Links County Offices \| Departments

Publications Soil Erosion and Clear Streamwater

Publications
Soil Erosion and Clear Streamwater