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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.”
Intense rainstorms stripped fertile soil from unprotected farm fields across the Corn Belt last spring. Parts of east-central and northwest Iowa lost as much as 24 tons of topsoil per acre in May, according to Daily Erosion Project estimates. “It’s been pretty dramatic,” says Matt Helmers, Iowa State University Extension biosystems engineer. Even in fairly flat areas, “we’ve seen a lot of ephemeral gully erosion.”
Richard Cruse, director of the Iowa Water Center, adds, “Heavy rains came at the worst time this year, when nothing was planted and there was no surface cover.” Many grass waterways, which slow water flow, have been torn out in recent years, and “many others are degraded or not functioning well. This spring shows what can happen as a result.”
The damage underscores the need for conservation practices that protect the soil and slow down water flow during storms, says Dennis Frame, University of Wisconsin Discovery Farms director. “This is a perfect year for farmers to evaluate their conservation programs. You can really see where you should have a grass waterway or buffer strips.”
To minimize future losses, Frame says, understand when and where runoff and soil erosion are most likely to occur, and how you can lower their risk.
Erosion factors are listed below along with erosion risk.