Just how much can you lower soil erosion losses on one site by changing tillage practices and cropping methods? David Harrell, Johnson County SWCD, recently used the most commonly accepted soil erosion equation to answer that question, based on 20 acres common to his area.
Soil types included gently to strongly sloping Miami soils, with more level Crosby soils also in the mix. The previous cropping system was corn and soybeans in rotation with a chisel-plow system. When he ran the numbers, even Harrell was amazed.
Under its current use, soil loss was estimated at somewhere between three to four tons per acre per year, depending largely upon soil type. If the area was converted to permanent hay or grass, soil losses fell to well under one ton per acre per year, sometimes to under 0.3 tons per acre per year. Not everyone wants to convert farmland to hay or grass, especially not now. But the ability of changes in erosion and cropping methods to put the clamps on soil erosion.
Actually, Harrell made the calculation on a parcel of land soon to be converted to a high school cross country course. The entire area will be converted into grass - one type where the runners will actually run, and a more normal type for the area covering the rest of the property.
Not all urban development is this environmentally friendly, of course. The typical subdivision brings houses and lots of pavement, as does a shopping center development. Runoff from pavement can include pollutants. Developers also have to often construct retention or detention ponds to deal with the flow of water off of impermeable materials, like sidewalks, building roofs and parking lots.
Yet this one example does illustrate how much changing to an environmentally friendly land use can affect the sediment running off into a stream. Sediment is still the number one pollutant of Indiana streams, rivers and lakes, experts say. Sediment refers to soil particles. They also carry off nutrients and pesticide particles that attach to the soil.
While the example wasn't done to advocate turning all farm fields into grass, it did illustrate that making changes, even going to more intense conservation tillage that leaves at least 30% residue on the surface at planting in the spring, can greatly reduce soil erosion, especially on sloping fields and other areas subject to soil erosion.