President Franklin D. Roosevelt.
A letter sent to Governors on February 26, 1937.
|Natural Science 101|
Cropland and Erosion
Conditions in Texas
Types of Soil Erosion
Cropland Erosion and Surface Water
Soil Erosion Abatement Programs
Soil Conservation Practices
Almanac Table of Contents | Chapter Five Table of Contents | TEC Home Page
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Soil is the material that is formed from rocks and decaying plants and animals; it makes up the outermost layer of the earth. There are at least 70,000 kinds of soil in the United States. Topsoil is considered the most productive soil layer. According to the United States Department of Agriculture, natural processes can take 500 years to form one inch of topsoil.(1)
One of the first steps Congress took was to create the Civilian Conservation Corps, which put unemployed men, including farmers, to work planting trees and building erosion control dams. In 1935, the Soil Conservation Service was established within the United States Department of Agriculture and began to work directly with farmers around the country creating soil and water conservation districts. Soil and Water Conservation Districts are political subdivisions of the state, governed by a board of directors elected by resident landowners of the district. Some of the soil erosion correctives recommended in the 1930s included crop rotation, contour plowing, planting tree rows and leaving marginal lands as pasture land. These practices were credited with arresting soil erosion for a time.
Texas enacted its own Soil Conservation Laws in 1939, resulting in the establishment of the Texas Soil and Water Conservation Board. The Board coordinates the activities of the local soil and water conservation districts, which numbered 213 in 1994.
In the 1970s, an increase in worldwide demand for farm commodities led the U.S. government to create new crop subsidy incentives to persuade farmers to plant "fencerow to fencerow." Farmers eager to increase production put marginal lands into production and discontinued the practice of crop rotation. To combat the depletion of overused soils, farmers had to increase their use of chemical fertilizers. By the mid 1980s, new federal action was needed to confront the problem of soil erosion. The current Food Security Act of 1985 (aka the 1985 Farm Bill) contains two major features, informally called the "sodbuster" programs, that address soil erosion. The Conservation Reserve Program (CRP) pays farmers to take highly erodible land out of production for 10 years. The Conservation Compliance Provision (CCP) requires farmers with highly erodible land to implement approved conservation plans by December 31, 1994, to be eligible for any federal farm program benefits.
Large scale loss of soil from erosion results in at least two major environmental problems. First, cropland becomes less productive because the soil left after erosion loses its fertility and is unable to supply plants with necessary nutrients. The soil's ability to retain water is also greatly diminished. These changes, in turn, result in higher production costs, including the costs for the increased use of petrochemical-based fertilizers. Second, soil erosion by water causes sedimentation in waterways which threatens aquatic life and hinders the water flow. Soil erosion by water also carries polluting agricultural chemicals into rivers, streams, lakes and reservoirs. According to a 1989 study conducted by the National Academy of Sciences, 350 to 400 million acres of agricultural land are estimated to account for more than 50 percent of suspended sediments deposited in surface waters in the United States.(3)
Experts recognize the difficulty in accurately assessing costs of soil erosion, but the USDA has estimated that the offsite costs to society of erosion in the United States are between $2 billion and $8 billion annually, and the direct onsite farm cost is estimated at $1 billion to $18 billion per year.(4) The United States Department of Agriculture, however, has expressed doubts about the reliability of these estimates.
WIND EROSION ON CROPLAND
Of the 32 million acres of cropland in Texas, more than 12.8 million acres or 40 percent are classified as highly erodible.(5) With an average loss of 14 tons of soil per acre annually, Texas is one of the eight worst states for soil erosion rates.(6)
Water erosion is the primary concern for the central and eastern parts of Texas. Wind erosion is the primary concern in far west Texas and the High Plains region. Both wind and water are concerns in the Rolling Plains and southern parts of the state.
The Federal and State agencies that have major responsibility for the well-being of our soil are:
Soil erosion levels vary among types of soil, and, of course, some erosion is natural and inevitable. The amount of soil erosion that most cropland can tolerate without reducing production is termed by the United States Department of Agriculture the "T" factor. In Texas, the "T" factor for most cropland is about five tons per acre per year.(10) Most Texas cropland can lose five tons of soil a year for an indefinite period of time without production being affected. The objective of conservation practices is to bring erosion down to or below this "T" factor.
According to the Texas State Soil and Water Conservation Board, total gross sheet and rill erosion within Texas averages about 229 million tons annually. This is an average annual rate of 1.36 tons per acre. Gross gully and stream erosion averages about 98 million tons annually, or an average rate of 0.58 tons per acre.(11)
Soil erosion by water is a problem on about 24.3 million acres of Texas cropland and grassland.(12) Figures are not available on the number of acres on which wind erosion has a large impact.
WATER EROSION ON CROPLAND
|SURFACE AREA AND LAND COVER/USE OF TEXAS|
|Surface Area of Texas||170.8 million acres|
|Federal Land||3.0 million acres|
|Census Water/1*||3.8 million acres|
|Nonfederal Land||164 million acres|
|Urban and built-up land, rural transportation land and small water areas||7.2 million acres|
|Rural land||156.8 million acres|
|Cropland||32 million acres (20%)|
|Rangeland||95.2 million acres (61%)|
|Forestland||9.5 million acres (6%)|
|Pastureland||17.7 million acres (11%)|
|Minor land cover/uses||2.4 million acres (2%)|
|*Census Water/1: the surface area of inland bodies of water larger than 40 acres and of perennial streams wider than 1/8 mile.|
Source: Texas State Soil and Water Conservation Board. A Comprehensive Study of Texas Watersheds and Their Impacts on Water Quality and Water Quantity, January 1991.
|TYPES OF SOIL EROSION|
Soil erosion is caused by wind and water. There are four basic types of water erosion.(9)
Sheet Erosion. The removal of a fairly uniform layer of soil from the land surface by the action of rainfall and surface runoff.
Rill Erosion. The formation of numerous small waste channels, occurring primarily on recently cultivated soil.
Gully Erosion. An advanced state of rill erosion in which water accumulates in channels and washes away soil to depths ranging from one to two feet to as much as 75 to 100 feet.
Streambed Erosion. The widening of streams.
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