How to Make Cover Crops Work in Montana

Water is a precious commodity in Montana cropping and livestock systems, where annual rainfall amounts can range from 6 to 22 inches, depending on the region. It is a challenge to grow cover crops and take advantage of their potential benefits, such as weed suppression and improved soil quality, without draining that crucial resource. 

“We’re always kind of guarding our water – saving our water – for the next crop,” as Montana State University cropping systems agronomist Dr. Perry Miller puts it. But MSU researchers, including Dr. Miller and Dr. Kent McVay, have devoted years to studying how cover crops can fit into this state’s unique agricultural systems, and their research is yielding valuable insights.

Watch the video below to hear them explain how cover crops affect wheat yields, crop rotations and livestock in their regions to Dr. William Curran, a Penn State emeritus professor of weed science.

The Wheat Yield Trade-Off

Fallow wheat fields, a common water-preservation tactic, crisscross the Montana landscape. (Photo credit: Kent McVay, MSU)

In central and eastern Montana, it’s common to place a period of summer fallow between two winter wheat crops, in an effort to preserve moisture and soil resources. That’s an obvious place to try to insert cover crops, Dr. Miller says. 

But it can come at a cost. 

In a dry year, a summer cover crop has been shown to drop the yield of a following wheat crop by up to 50%, the researchers note. Even when Mother Nature is more generous with rainfall, wheat yield losses can still hover between 20 and 30%. 

Spring pea covers are an option for Montana growers. (Photo credit: Perry Miller, MSU)

However, peas have proven to be a less water-hungry cover crop, Dr. McVay says. His research has found that a summer cover of peas may only drop wheat yields by 10% in a normal-to-wet year, while also providing valuable nitrogen and weed suppression. 

Moreover, growers who lose a whole year of wheat yield to a fallow year should note that switching to a Winter Wheat – Spring Peas – Spring Wheat rotation actually adds another year of wheat yield, however reduced it may be by the cover crop, Dr. McVay adds. 

Forage is a Good Fit

Finally, cover crops can also serve as a summer forage option in Montana, which can provide an additional value that may offset those yield losses, Dr. Miller says. 

“There’s a strong need for alternative forage use periods,” he explains. As a result, cover crop acres in the state likely overlap significantly with forage use areas. 

 “These cover crops can be pretty profitable as a grazing alternative,” Dr. Miller says. 

See more from GROW on integrated weed management and herbicide-resistant weed challenges in Montana here. Learn more about using cover crops for weed management here.

Video, feature photo and header photo by Claudio Rubione, GROW; video contributions by Bill Curran; text by Emily Unglesbee, GROW