Improving Soil Health Reduces Erosion
By Jason Johnson, USDA-NRCS, Iowa
From drought to flood conditions, it seems there is no longer a “normal” growing season for Iowa farmers. A year of drought in 2012 was followed by a cool, wet spring this year. These types of weather extremes can be very damaging to Iowa’s soils, but conservationists are finding that farmers who apply soil health practices like cover crops are the least affected.
Besides cover crops, conservation practices that improve soil health include no-till, crop rotations, and responsible nutrient and pest management applications.
Several southeast Iowa counties received six to eight inches of rain on April 17. Shawn Dettmann, area resource conservationist for USDA’s Natural Resources Conservation Service (NRCS) in Fairfield, says soil health practices combined with erosion control practices – like contour farming, terraces, contour buffer strips and grassed waterways – provided the most protection from erosion caused by heavy rains.
“In fields where soil was disturbed through tillage, there are some rough areas with a lot of soil erosion,” said Dettmann. “In fields with high amounts of crop residue and little to no tillage, there was significantly less erosion, and in fields with these practices plus cover crops, there was little to no erosion.”
Iowa farmers planted about 100,000 acres of cover crops in fall 2012, which Dettmann says will undoubtedly help reduce the impact of heavy spring rains. “We (NRCS) are promoting cover crops to increase soil organic matter and water infiltration rates, and to limit nitrogen leaching,” he says, “but erosion reduction is an additional benefit during heavy fall and springtime rains.”
One farmer who reaped the erosion control benefits of cover crops is Don Swanson of rural Ottumwa. His 28 cover crop acres protected the soil very well after receiving more than six inches of rain. In areas where he has no-till fields with terraces – but no cover crops – erosion was visible. “Our six-inch rain felt more like 10 inches. It just flows so fast,” he said. “The first three inches of rain were welcome, but after that it was a mess.”
In Wapello and Davis Counties, NRCS District Conservationist Lori Altheide says farmers planted more than 5,000 acres of cover crops in the fall with assistance from USDA’s Environmental Quality Incentives Program (EQIP), and they planted many more on their own. “Ironically, many of our farmers used 2012 drought assistance funding to plant cover crops to help feed the soil and to take up excess nitrogen in the soil,” she said. “This spring those cover crops are also protecting the soil from erosion.”
Barb Stewart, state agronomist for NRCS in Iowa, says the “cover” that cover crops provide is only part of the erosion control benefit. “Any ground cover protects soil from taking a beating from the force of falling raindrops,” she says. “Crop residue and living plants protect soil aggregates from disintegrating under the hammering energy of raindrops.”
Stewart says cover crops provide food for microorganisms, which in turn provide “sticky” substances that stabilize soil aggregates. “This also improves water infiltration and aeration,” she says.
For more information about practices to help improve soil health, visit your local NRCS office or go online to www.nrcs.usda.gov.