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May Rains Erode Western Iowa FieldsJune 6, 2007
For the second time in four years hard May rains on the long, steep slopes of western Iowa resulted in damage to hundreds of thousands of cropland acres. Counties as far north as Ida County to Fremont County in far southwestern Iowa received more than ten inches of rain in May. A total of 14 counties in this region were drowned by more than ten inches of untimely rains, actually exceeding the 2004 May rain total, the last time this area was hit hard. Conservationists with the USDA’s Natural Resources Conservation Service (NRCS) in western Iowa surveyed cropland for damage. They all reported a similar theme – cropland that had been tilled showed the most signs of soil erosion and fields with complete conservation systems, not just one practice, showed the least damage. Greg Mathis, district conservationist in East Pottawattamie County, said it was obvious that no-till fields sustained less damage. “Those fields with corn stubble still standing were hardly damaged at all,” he said. “Fields with bean stubble and no-tilled faired pretty well, while tillage allowed for massive soil movement." “Sheet and rill erosion occurred where there was tillage,” said Angela Biggs, district conservationist in Shelby County. “Fields that were no-tilled with well-maintained field borders held up better with less visible signs of erosion.” In Union County, District Conservationist Paul Goldsmith observed that no-till or conservation tillage fields protected with well-maintained conservation practices, like terraces and grassed waterways, suffered very little erosion damage. “Fields that had pretty heavy tillage experienced severe erosion,” he said. “There are several fields in the county that sustained soil losses of more than 20 tons/acre in just one weekend storm.” Goldsmith also noted that rows planted up and down steep slopes resulted in heavy erosion. “This was especially evident where anhydrous had been applied up and down the slope,” he said. Harrison County’s flooding damages have been well-documented. District Conservationist Russell Kurth said they had seven to ten inches of rain in one night, after the ground was already saturated, producing a lot of runoff. “It takes a combination of conservation practices to do the job,” he said. “Fields with no-till, terraces and planting on the contour had the least amount of damage.” NRCS officials also reported damage to conservation practices, such as terraces and grassed waterways. “The key is to keep practices maintained,” said Biggs. “Do not farm up and down along the side of grassed waterways. This causes water to run down the outside of the waterway, creating gullies.” Biggs also said it is important to mow grassed waterways, keep trees out of terraces and remove sediment build-up and trash from around terrace in-takes.
Mathis said broken out terraces were speckled throughout the affected area. He said most producers will have to wait until fall to repair them. Mathis, however, is more concerned with gully erosion. “The tendency may be to disk out ruts in the fall after harvest, but this creates an environment for a rain event to wash it out again,” he said. “It may be better to plant a temporary seeding of rye grass in the fall.” Goldsmith suggests farmers observe the damage heavy rains created to learn where future conservation practices may be needed. For example, where a gully has formed, a grassed waterway may be needed. “Where good conservation practices were not in place, erosion was evident,” he said. “These would be areas where producers may want to install conservation measures to protect them in the future. Producers should also take note of conservation practices that need maintenance or had some siltation damage.” Contact your local NRCS office or visit www.ia.nrcs.usda.gov today about conservation practices and programs to protect your land from soil erosion and sediment runoff or to improve your water quality. -30- Contact: |
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