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|Sedimentation is usually the end result of the erosion process. When a soil particle is detached and transported by water to a new site of deposit, it is referred to as sediment. The soil particle might be temporarily deposited several times before it reaches its end destination.|
Cropland erosion has impacts on more than agricultural production. According to studies conducted by the USDA in 1987, agriculture accounts for more than "50 percent of suspended sediments from all sources discharged in surface waters" and greater proportions in predominantly agricultural regions.(13) Findings of a nationwide study conducted from 1974 to 1981 concluded that surface water sediment deposition was "significantly related to cropland erosion within basins. It was not closely related to estimates of total basin erosion from forest land, pasture land or range land."(14)
The increased murkiness in the water caused by sediment loading decreases light for submerged aquatic vegetation. As a result, both aquatic vegetation and species that depend on aquatic vegetation for breeding and food can decline.(15) The relationship between sediment and nutrient runoff from agricultural lands and their effects on estuaries is discussed in the water chapter. Sediment loading can also fill reservoirs, clog navigable waterways, reduce recreational use of waters and increase operating costs of water-treatment facilities.
Some sediment deposits can be beneficial, however. For example, the replenishment of beaches is dependent upon sediment deposits from rivers.
The USDA estimates that putting 30 to 40 million acres of highly erodible U.S. cropland out of production and into the Conservation Reserve Program will reduce sediment delivery to surface waters by as much as 200 million tons per year.(16)
Texas has no data that show whether various erosion control strategies have reduced sedimentation in Texas surface waters. The Texas State Soil and Water Conservation Board states that "soil erosion and sediment production continue to be major problems in Texas," though it speculates that there has been significant improvement in the last few decades.(17) The Board, lead agency for non-point source pollution from agriculture, has recommended expanded stream and reservoir sedimentation studies, stating that past studies have been incomplete.(18)
According to the Texas Water Development Board, sediment buildup in reservoirs has not caused a major water supply problem to date, but the agency continues to monitor the situation. The TWDB studies show that Lake Buchanan in Central Texas does have noticeable amounts of sediment as does Lake Corpus Christi.(19)
In Texas, average annual sediment yields - that portion of the total eroded soil that reaches a reservoir - vary from one land resource area to another and vary within land resource areas. According to a USDA study, sediment yields have varied from a low of 0.6 acre-foot per square mile at a site west of Lampasas to a high of 8.60 acre-feet per square mile at a site northeast of Bowie in Montague county.(20)
HIGHLY ERODABLE CROPLANDS IN TEXAS
One of the best treatments for highly erodible land is to take it out of production and plant grass cover.(21) To speed this practice along, the 1985 Farm Bill's Conservation Reserve Program (CRP) was formulated to provide financial incentives to farmers who voluntarily take highly erodible cropland and other environmentally fragile land (e.g., wetlands, wildlife habitat) out of production for ten years. This means no haying, grazing or harvesting of the land. Though there is a 25 percent cap per county on the amount of land that can be eligible, the program does provide farmers with the opportunity to receive $40 per acre per year rental fee to retire land and a 50/50 cost-share payment to plant a permanent soil-conserving cover.(22)
Cropland retired under the CRP was eroding at 13 tons per acre per year. After taking it out of production and establishing coverage, the rate of erosion is 2 tons per year.
With 4.2 million acres - 12 percent of all cropland - in the Conservation Reserve Program, Texas has more land in the program than any other state.(23) (Due to the amount of cropland in production, Texas, of course, has more potential acres to be in the CRP.)
In 1993, Texas producers received $164 million in rental fees, and approximately $100 million in cost sharing from the inception of the program in 1986 to 1993 in return for taking more than 4 million acres out of production and converting it to grass. The average one-time cost share for establishing grass cover is $25 per acre. More than 80 percent of the CRP acreage is in the High Plains and Rolling Plains. Reduced erosion - an estimated 22 percent reduction on U.S. cropland since 1985 - is not the only benefit of the Conservation Reserve Program. Environmental benefits include improvement in air and water quality and an increase in wildlife habitat for game and nongame birds, mammals and reptiles. Soil conservation specialists in Terry and Lubbock counties report a noticeable reduction in wind erosion and change in air quality as well as an increase in wildlife since cropland has been enrolled in the CRP.(24) The Environmental Working Group notes that the CRP has saved the state 144.8 million tons of soil annually.(25)
The Wall Street Journal reports that the CRP program has its critics. The average age of landowners participating in the program is 64, leading some to believe that it is a "welfare plan" for retired farmers. Others complain that too much good farmland has been allowed in the CRP program. Meanwhile, there are residents of the Texas Panhandle who complain that taking 20 percent of the Plains farmland out of production has devastated related businesses, such as cotton gins and seed, pesticide and equipment dealers.(26) There has also been criticism about the high cost of the CRP. CRP proponents suggest, however, if farmers who are currently enrolled in the CRP were growing rice, cotton, grains and other crops eligible for income supports, their deficiency payments would be equal to, if not more than, the CRP costs.(27) In addition, the USDA estimates the CRP's environmental benefits at between $6 billion and $13 billion over the life of the contracts.(28)
Unless extended, the CRP program will begin to phase out in 1995. Much of the acreage now enrolled in the CRP will revert to row crop and forage production. A study conducted by Texas Tech University's Department of Agricultural Economics found that, in 55 counties in the Plains, economic considerations will encourage farmers to return 64 percent of the land to crop production unless the CRP is extended.(29) This is not just the prediction for Texas; according to the Soil and Water and Conservation Society the return of CRP land to production will occur nationwide.(30) A revised CRP program that targets truly erodible land for inclusion might be presented to Congress in 1995.
The other major erosion-abatement provision created by the 1985 Food Security Act is the Conservation Compliance Provision. This provision required farmers who had highly erodible land and who wanted to retain eligibility for government program benefits to implement a conservation plan and have it approved by the Soil Conservation Service by December 31, 1994.(31)
Conservation tillage is one good example of mature conservation practices.(32) According to the Conservation Technology Information Center, a not-for-profit organization that provides research on soil conservation, 22.4 percent (4,482,961 acres) of Texas cropland is in conservation tillage.(33) Conservation tillage is expected to increase as a means to meet the requirements of the conservation compliance provision, but experts suggest that continued research is needed to better understand its effects and to determine which types of crops respond best.(34)
|SOIL CONSERVATION PRACTICES|
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