Farm and Field

Study: Long-term crop rotation reduces greenhouse gas emissions

Posted: Jun. 24, 2018 12:01 am

Many farmers grow corn and soybean in rotation to avoid the continuous corn yield penalty, but now there's another reason to rotate.

Scientists at the University of Illinois have provided further evidence that rotating crops increases yield and lowers greenhouse gas emissions compared to continuous corn or soybean.

"I think farmers in today's world are looking for reasons to avoid growing in a monoculture. They're looking to diversify and rotate their systems. If they're doing that partially out of a concern for the environment, well, it lowers greenhouse gasses. And it could potentially result in a substantial yield increase," said Gevan Behnke, research specialist and doctoral candidate in Maria Villamil's research group in U of I's Department of Crop Sciences.

Behnke sampled greenhouse gas emissions from fields that had been maintained as continuous corn, continuous soybean, rotated corn-soybean or rotated corn-soybean-wheat, under tillage and no-till management, for 20 years.

Comparing the corn phase of a corn-soybean rotation to continuos corn showed an average yield benefit of more than 20 percent and a cumulative reduction in nitrous oxide emissions of approximately 35 percent.

Nitrous oxide is an extremely potent greenhouse gas, with a global warming potential -- how much heat a greenhouse gas traps in the atmosphere -- almost 300 times higher than carbon dioxide.

For soybean, which doesn't get fertilized, rotation did not affect nitrous oxide emissions compared to continuous soybean, but rotation did increase soybean yield by about 7 percent.

Tillage did not impact greenhouse gas emissions, but the practice gave corn an edge of about 15 bushels per acre over corn in no-till management. Behnke said that effect may not apply to farms outside the study area. The study was conducted at the Northwestern Illinois agricultural Research and Demonstration Center near Monmouth. With some of the most productive soils in the world, Behnke said corn yields are higher there than almost anywhere else -- and greater yields mean more surface residue.

Fire ants

Missouri livestock producers may be looking south for hay due to concerns over predicted hay shortages, but buyer beware of red imported fire ants hitching a ride.

The invasive species attacks native insects, birds, reptiles and small animals. When disturbed, they will defend themselves against livestock and humans with a vicious sting. The sting contains a venom that causes intense burning and itching.

While the stings are painful, less than 1 percent of people need medical attention from being stung by red imported fire ants.

Fire ant were unintentionally introduced in Alabama from South America in the 1940s. Entomologists report them in 13 states, and few predators attack them. The good news, University of Missouri Extension field crops entomologist Kevin Rice said, is that they do not survive Missouri winters.

Bales crossing state lines should be inspected and certified by U.S. Department of Agriculture or state regulatory officials. Also, Rice suggests that buyers visually inspect each bale for fire ants. Place baits such as hot dogs or peanut butter next to bales for an hour and then scout.

Red imported fire ants measure 1/8- to 1/4-inch long and can be distinguished from other ants by a two-segment petiole (or waist) and 10-segment antennae that end in two-segment clubs, Rice said. The reddish-brown ant bears a distinctive stinger at the tip of the abdomen.

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