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Mark Riechers and his son Joe raise corn, soybeans and cattle on rolling slopes near Darlington in southwestern Wisconsin’s Driftless Area. Their erodible loess soils have been in continuous no-till for more than 20 years. After two decades without being disturbed, the soil is rich with what Mark calls “dirt critters,” the beneficial organisms that build soil structure and tilth. “Because we don’t disrupt the soil structure with tillage, it can take a lot of water,” he says.
As a result of their farming practices, which also include grass waterways and multiple thin applications of solid manure, just 2% of annual rainfall ran off the Riechers’ farm, according to 7 years of monitoring by the University of Wisconsin Discovery Farms. Sediment losses averaged about 300 pounds per year, or 3% of NRCA “tolerable” loss. “It’s not just no-till,” Mark says, “it’s a combination of things.”
2. Structures that slow water flow
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Ephemeral gullies form when rainwater flowing over a field concentrates into narrow channels, which then transport field runoff laden with soil and nutrients. When closed with tillage, they reappear with the next big rainstorm.
One of the best ways to halt ephemeral gully erosion is to plant grass waterways in areas of concentrated flow, Frame says. “Grass waterways are critical,” especially on long slopes with clay soils. When you evaluate this spring’s erosion toll, “The first thing you should think about is, do you have adequate grass waterways? Are they big enough? Are they in the right place?”
Sediment-control basins or dams placed across the channel are also good at slowing down water, he says, lowering its erosive force, and allowing soil to drop out. Water pools briefly behind these earthen berms — some of which are broad enough to be farmed over.
Another effective way to slow water flow and soil loss is planting vegetative buffer strips in strategic places within cropped fields or at the foot of slopes.
Helmers leads research on the use of “prairie filter strips” on 6-10% slopes in central Iowa. Planting strips of grasses, forbs and legumes at the bottom of sloping no-till corn and soybean fields trapped 96% of sediment, he says. (See http://bit.ly/STRIPs for more information.) “Prairie filter strips could be even more effective in more intensive tillage systems such as chisel plow,” Helmers says.