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Bill and Babetta Lucke of Persia, Iowa, battle extreme weather, like so many farmers recently. As 12-year no-till veterans with terraced slopes and miles of grass waterways, the southwest Iowa farmers have a new twist on conservation. Instead of disking field gullies closed, Bill uses an 8-yard scraper to push soil back up hills to fill field gullies. It takes some time to pack it so it doesn’t move, but it’s well worth it, he says. Filled with fertile topsoil that has washed downhill over the decades, the repaired gullies “sometimes yield better than the rest of the field.”
Extreme weather finds even longtime no-tillers fighting washouts and erosion. Bill and Babetta Lucke of Persia, Iowa, 12-year no-till veterans, have a stellar soil-saving system, including terraced slopes and miles of grass waterways. “These things help a lot,” Bill says, but with torrential rains and the 2012 drought, “we still lose some soil.” Buffeted by weather extremes like so many Corn Belt farms, their 1,000 acres lie in the fertile loess hills of southwest Iowa.
The most effective way to slow your topsoil and keep it in place is less tillage, says Iowa State University (ISU) Extension Field Agronomist Clarke McGrath, in southwest Iowa. “Nothing can prevent all soil erosion, but established no-till fields will have better erosion resistance and water infiltration than minimum-till fields, and minimum-till fields will be better than conventional till.”
Worst erosion in 25 years
In 2012, several factors combined to cause “the worst erosion I’ve seen in 25 years, especially in southwest Iowa,” McGrath says. There was more tillage than normal due to compaction problems, glyphosate-resistant weeds and more continuous corn. Even shallow tillage loosens soil and residue, he says. “In southwest Iowa, that’s not working as well as no-till to reduce soil erosion.”
The 2012 drought raised erosion risk in many places. Drought-stricken crops produced less and more fragile residue, exposing more soil surface to the elements in this recent more variable and extreme weather.
Persistent drought also weakens soil structure, says Mahdi Al-Kaisi, ISU agronomist. That’s because microbial activity, which builds soil aggregates, slows down when it’s dry.
Meanwhile, intense rains have become more common – summer of 2012 aside, McGrath says. “Our rainstorms the last five years have gotten increasingly severe.” In a pounding storm, raindrops can hit the ground at 20 mph, splashing as high as 4-5 ft., Al-Kaisi says. Splashed soil particles “clog surface pores, which in turn reduce water infiltration, increase water runoff and increase erosion.”
The problem is worst in fields with poor residue cover. Soils with little residue are also prone to crusting after hard rains, he adds. In addition, these crusts “create conditions extremely conducive to soil erosion following rainfall events.”
In the Corn Belt, 70% of highly erodible cropland – more than 14 million acres – is losing soil faster than the NRCS’s “tolerable” rate of 5 tons/acre/year, according to the 2007 NRCS National Resources Inventory, its most recent. And that percentage has barely budged since 1992. NRCS considers about a quarter of the Corn Belt’s cropland to be highly erodible.