Madison County Soil Conservation District
Serving to Conserve Madison County's Soil & Related Natural Resources Since 1941
The District's primary concern has been soil erosion. Soil erosion results from several factors, including amount and intensity of rainfall, slope length, slope percent, soil characteristics, and ground cover. Soil erosion starts with impact erosion caused when rain drops crash into the earth. Without adequate cover rain drops will dislodge soil particles and carry them several feet in all directions. As the rain continues water mixed with soil collects and begins to run downhill. The small streams create rill erosion across the fields. As the rain continues and intensifies the rills form sheets of water wherein soil is eroded uniformly within the sheet causing thin sheets of soil to erode known as sheet erosion. The sheets of water converge on the valley floor where the water is concentrated causing deep gully erosion. Although gully erosion is most dramatic, sheet erosion often causes the most damage to cropland. Over several years the many thin sheets of soil that have been eroded away will reduce the overall productivity of the soil.
The easiest and most effective way to reduce soil erosion is to increase ground cover. Ground cover can be increased by converting cropland to grass or trees, improving forage stands, no-tilling, reduce tilling, and by planting cover crops after harvest. Below is a picture taken at the NRCS booth at the Milan No-till Field Day. The demonstration shows that the more ground cover the more infiltration and the less runoff.
From left to right the ground cover is reduced from sod with near 100% cover to conventional tillage with near 0% cover. The demonstration shows that with sod there is practically no runoff and lots of infiltration as compared to clean tillage where there is practically no infiltration and a lot of runoff. The cause of this vast difference is due both to the amount of ground cover and with the different soil structures resulting from different tillage practices.
Below is picture taken at the NRCS booth at the Milan Field Day. The picture is of a slake test which shows the affect soil structure has on the ability of soil particles to cling together with the rapid introduction of water. Two soil clumps were taken, each relatively dry. One from a field that had been no-tilled for years. The other from a conventionally tilled field. The soil clumps are suspended in separate containers of water. The tilled soil which has practically no soil structure started breaking down immediately while the no-tilled soil with excellent soil structure, including lots of air pockets, remained almost 100% intact.
You can view an actual demonstration on You Tube showing the effect tillage has on soil structure and the effect soil structure has on water infiltration and storm runoff.
Another soil concern is development. Each year thousands of acres of highly productive soil is converted from cropland to other uses. Once soil is taken out of production it is unlikely it will ever be used to grow food or fiber. From 1982 to 2007 there were 14 million acres of prime farmland converted to other uses in the U. S., an area half the size of Tennessee.
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