On the surface, a bit of cereal rye doesn’t look like much. In years of rapid flooding, though, it has paid dividends on low ground, says George Schaefer, who farms with his brother, Steve, near Kalona, Iowa.

“Just that little bit of cereal rye has held residue,” says Schaefer. He covered this topic and others at a Practical Farmers of Iowa (PFI) field day earlier this month.

Purdue University and NRCS scientists agree. In a news release earlier this week, they note that cover crops can help preserve healthy soil in this year’s unplanted flooded fields. That’s according to a new article by Purdue agronomist Eileen Kladivko and Barry Fisher, Indiana state soil health specialist for the Natural Resources Conservation Service.

“These prevented-planting acres, while unfortunate for this year’s production, should be managed in ways to prevent further soil degradation and to increase soil productivity for next year,” the authors write. “Cover crops are an excellent option for producers to consider for protecting their soil and increasing productive capacity for succeeding years.”

Excessive rainfall, like much of the Midwest has experienced this month, can break down soil aggregates, especially near the surface, Kladivko and Fisher note. Flooding and erosion can wash away nutrient-rich topsoil. When fields dry out, the remaining soil is baked to a hard crust that is susceptible to further erosion by wind and rain.

Long-term, cover crops can also help rebuild soil organic matter. Perks include better water infiltration and reduced compaction and surface crusting.

“In pioneer days, (Iowa) soils used to have 6% to 7% organic matter,” says Steve Berger, a Wellman, Iowa, farmer, who also spoke at the PFI field day. Nowadays, many Iowa fields have one-half that level.

Cover crops can help rebuild those soils. Slowly.

“Over time, it will build organic matter on the level at .1% to .2% per year,” says Berger.

Timely N applications are also paramount. Soil microbes thrive at a 24:1 C:N ratio (24 parts carbon to 1 part nitrogen). Some cover crops are higher than that. For example, straw from a rye cover crop has an 82:1 C:N ratio. To consume the high carbon content, soil microbes need to find more N.

That means that it’s important to make sure corn doesn’t run short of N if you’re pairing them with cover crops.

Allelopathy is often blamed for causing pale and stunted corn when cover crops are used. Berger, though, thinks it is caused by N deficiency. That’s why it’s important to regularly apply N and/or manure in increments throughout different parts of the year.

“Microbes need nitrogen to devour carbon,” says Berger. “You do not ever want corn to get short of N. You can’t show up at planting to apply N and think it will solve problems.”

For more information on the Purdue article, go to https://ag.purdue.edu/agry/extension/Documents/PreventedPlantingCovers20....