Wet spring battered soils in parts of Midwest
Although flooding in the Midwest this spring has not been comparable to the devastating floods of 1993 and 2008, this year’s deluge has battered cropland soils throughout the region, sending it into ditches and streams, according to a new report from the Environmental Working Group.
EWG released a new report this month, “WASHOUT: Spring Storms Batter Poorly Protected Soils and Streams” that showed the dramatic impact on the region’s fertile soils after multiple storms pummeled the region this spring. The report focuses mainly on Iowa, but eastern parts of the Corn Belt have likely not escaped soil erosion this year either.
Spring 2013 has been considered the wettest spring on record, according to the report. Iowa State University’s Iowa Daily Erosion Project (IDEP) shows how heavily damaged Iowa’s soil and streams were affected after five days of heavy rain in late May.
“In 50 townships covering 1.2 million acres, farmland suffered average erosion of more than 5 tons per acre over that five-day period,” according to the EWG report. “In 15 of those townships encompassing 346,000 acres, fields suffered average erosion of 7.5- to 13 tons per acre—far more than the annual rate of 5 tons per acre considered ‘tolerable’ for most Iowa soils by USDA’s Natural Resources Conservation Service. In other words, those 1.2 million acres of farmland may have lost more precious topsoil in five days that what is tolerable over an entire year. And most soil scientists think that a truly sustainable rate of erosion is far lower.”
What’s more alarming is that IDEP data show that vulnerable and/or poorly protected farmland suffered the worst erosion. The data estimates that in 115 townships, the hardest hit fields lost more than 20 tons of topsoil per acre in less than a week. And in 16 townships, poorly protected fields may have lost a devastating 40 tons or more soil per acre that week, according to EWG.
The IDEP data covers only the state of Iowa, but the same situation is occurring throughout the Corn Belt.
EWG speculates that soil erosion and polluted runoff are actually worse than even the IDEP estimates, because the project cannot currently account for the erosion and runoff caused by ephemeral gullies. These gullies – called ephemeral because farmers refill them temporarily with tillage each spring – appear quickly when runoff water flows through the lowest parts of a field and cuts a channel through unprotected soil.