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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Figure. Cover crops were on display for attendees at the 32nd Annual NWIARDC Field Day.
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Cover crops: planting date and soil moisture considerations

Cover crops: From antiquity to the present. Cover crops are plants that are grown between cash crops with the purpose providing environmental services like soil and water conservation (Figure). Cover crops have been used by diverse people and cultures throughout history; from more than 3000 years ago in China, to Thomas Jefferson at the time of our nation's founding. More recently, concerns about soil and water conservation and government regulation have created a wave of cover crops adoption that has moved from the East Coast to the Midwest.

Agricultural research, primarily from the Eastern US, has shown that depending upon latitude, soil type, environmental conditions and cover crop establishment and winter survival, cover crops have the potential to provide diverse 'environmental services'. Dead or alive, cover crops can reduce soil and water loss through several mechanisms. Roots stabilize soil and above ground plant matter creates obstacles and winding paths, slowing the speed at which water both meets the soil and flows. Cover crops can also affect the nitrogen (N) cycle: grasses and brassicas can sequester soil N and legumes can fix atmospheric N. Depending upon the species, cover crops can provide forage for livestock, have weed control properties and/or help to alleviate the effects of soil compaction.

Costs and establishment challenges. Cover crops also carry costs and some risk. This fall, seed costs range between $10 and $46 per acre and aerial application costs range between $12 and $17 per acre. Corn and soybean planting date, soil moisture, and cover crop growth habits can pose challenges for cover crops establishment.

Because in a typical growing year corn and soybean physiological maturity and harvest take place long after the ideal time to plant cover crop seed, most cover crops must be aerially seeded into a standing crop. Dr. Joel Gruver, cover crops researcher and Assistant Professor of Soil Science and Sustainable Agriculture at Western Illinois University, says that the ideal time to plant cover crops into a standing crop is when at least 50 percent of the sunlight can reach the soil. The widespread acres of late planted corn and soybean in 2013 is likely delaying cover crops seeding.

Just like any cash crop, cover crops seeds require moisture for germination and stand establishment. Despite the heavy thunderstorms that ripped through portions of Warren, Knox and Fulton Counties early Sunday morning, much of Western Illinois, including Monmouth, remained dry. The last significant rainfall in Monmouth was at the end of July (Figure). This will pose a significant challenge to cover crops establishment in 2013.

Lastly, different cover crops species have different growth habits and life cycles. These characteristics influence the optimal planting date. In a typical growing year many grasses, legumes and brassicas can be seeded without freezing temperatures threatening establishment until the middle of September (Figure). While come of the cereals such as cereal rye, winter triticale and winter wheat can be seeded through the middle of October or into November (Figure).

Termination challenges. For those cover crops that survive the winter, in certain years termination can present significant challenges. Cover crops in wet springs have the potential to become a fierce weed and can form a 'wet blanket' that slows the speed of soil warming and drying. Cover crops must be terminated, either chemically or through tillage, before planting the cash crop in order for that cash crop to be covered under federal crop insurance programs.

Online cover crops resource. The Midwest Cover Crops Council (MCCC) is a group of federal and university researchers who seek to "significantly increase the amount of continuous living cover on the Upper Midwestern agricultural landscape". The MCCC website is a good resource for general cover crops information. This website also houses a Cover Crops Selector Tool which provides county-specific planting recommendations based on desired environmental services.

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