Using oilseed radish as a cover crop after winter wheat has been steadily increasing in popularity, especially in no-till production due to its large tap root that seemingly helps to alleviate soil compaction and aerate the soil.
It also winterkills, decreasing the need for additional herbicides in the crop rotation. However, University of Wisconsin Extension agronomists offer a word of caution for choosing radish as a cover crop on highly erodible soils.
"This past spring, we examined a no-till corn field in southeast Wisconsin which suffered significant erosion shortly after corn emergence," says Jim Stute, Rock County agriculture agent. "Radishes had been planted into wheat stubble in 30-inch rows last fall for the purpose of bio-tillage.
"Field observations suggest that the radishes did a good job of loosening the soil in rows, but that left it vulnerable to water erosion. Rills formed down the decomposing radish rows. Lack of surface cover and a sloping field allowed water to gain momentum and create larger wash-outs. Residue-cleared corn rows also provided a pathway for the water and increased soil loss."
Heidi Johnson, Jefferson County agriculture agent, says this observation is not meant to suggest that tillage radish should not be used as a cover crop, but it provides a cautionary note to growers.
"Using the radish as a sole cover crop on sloping or erodible fields may create this undesirable side-effect, especially if planted in wide rows with close spacings between plants," she says. "Oilseed radish planted as a part of mix of species, such as oats, may help to resolve some of these challenges by providing additional soil cover into the spring."
The agronomists add that it also provides a reminder that certain cover crops may work better in certain fields over others. Cover-crop selection should be based on its fit within the cash-crop rotation, but specifics of individual fields should also be brought into the selection process.
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