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Cover crops can help curb weeds

A recent survey from Iowa State University estimates that only 15% of Illinois farmers planted a cover crop between 2000 and 2005.

Key Points

• Cover crops can help control weeds in organic fields.

• In trial, no-till crops started slowly but came on strong at the end.

• Time constraints still keep many from exploring cover crops.


However, as government, consumers and farmers become more concerned with sustainable production methods, perhaps it’s worth brushing up on some of the latest cover crop research. Last year, Western Illinois University professor Joel Gruver examined cover crops in conjunction with three tillage systems on the WIU/Allison Organic Research farm in Warren County.

Gruver pitted conventional till vs. bio-strip-till vs. no-till. Each system’s soybean yields topped 50 bushels per acre. Gruver says soybean yields have historically been about 10 bushels lower in this particular field. Thus, the results speak for themselves.

In each tillage system, Gruver planted different cover crops in fall 2008, each with a specific goal.

With the conventional tillage system, an oat cover crop provided maximum organic material, which was incorporated prior to spring planting.

For the bio-strip-till system, Gruver planted radishes on the same 30-inch rows that were planted to soybeans in 2009. Between the rows, he planted oats. The “bio” designation comes from the radishes’ root system, which creates channels for the soybean root system to follow.

In the no-till system, Gruver planted a combination of cereal rye and hairy vetch. The hairy vetch did not establish, but the rye grew to about 6 inches before going dormant.

In the other two tillage systems, the cover crops winterkilled as expected. This wasn’t a problem, however, as tillage could be used to control weeds in these systems.

Near the end of May, Gruver’s team used a culti-mulcher to roll down 5-foot-tall cereal rye about a week before planting soybeans, which were put in with a no-till drill. Ten days after planting, soybean plants began to emerge through the rye.

In July, Gruver began to think he’d made a big mistake. The soybeans in the conventional and bio-strip-till systems looked good. However, the no-till soybeans looked “patchy,” and in some places, downright sparse.

In August, things began to look up. The no-till crop filled out nicely, leaving only a few places without a closed canopy. No-till plants with more space produced more pods. Harvest confirmed the extra pods compensated for uneven spacing.

The yields across the three systems were not statistically different: conventional, 55.2; bio-strip-till, 53.6; and no-till, 53.8. Not bad, especially considering the no-till system utilized only 2.7 gallons of diesel per acre, compared to the conventional system’s 5.2 gallons.

This was Gruver’s first experiment evaluating strategies for reducing tillage in organic farm systems. In 2011, he has plans for a no-till organic corn crop that relies solely on hairy vetch for nitrogen.

Gaining acceptance

Gruver realizes cover crops aren’t right for everyone. “The biggest challenge is timing,” he notes. “It’s hard to get a good stand if you wait until after harvest to plant cover crops.”

Some new technologies may be on the horizon to help minimize the time constraints. Aerial seeding into standing crops in late summer can work well, but it’s hard to get a uniform stand.

This year, a group of central Illinois farmers will experiment with a high-boy that drives through mature corn, dropping seed between the rows.

A third technology is a device that mounts just behind the combine header. As the farmer harvests, this piece of equipment throws seed.

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FILLED IN: As you can see, the no-till soybeans filled in nicely (right), despite patchy emergence. In the end, the three tillage systems produced similar results.

This article published in the April, 2010 edition of PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.