Weed specialist explains cover crops are a tool to compete with pests

On Feb. 3 during a Cover Crop Strategies podcast, University of Nebraska-Lincoln Weed Management Extension Educator Chris Proctor shares his thoughts on the advantages of cover crops.

Utilizing cover crops can be an effective tool when managing weed suppression as cover crops are able to compete with weeds for sunlight and water, he notes.

“It’s about resource competition,” says Proctor. “Cover crops can effectively suppress weeds and keep them from emerging or slow their growth down.”

Cover crops have the ability to change micro-environments where weeds are germinating, which can delay the time those weeds begin to emerge to a later part of the growing season. 

A recent study in Kansas, which utilized wheat as a cover crop, showed delayed palmer amaranth growth by 50 percent of emergence from mid-May to mid-June, Proctor shares. 

Cover crops also have the ability to reduce the density of weeds, he says, noting, “Fewer weeds tend to emerge where cover crops are present.”

Proctor reminds producers all weeds won’t disappear with the use of cover crops, but there will be fewer weeds emerging as they become less competitive.

“Cover crops compete for resources weeds might otherwise utilize. The faster producers can establish a cover crop, the more competitive it can be against emerging weeds,” Proctor says.

Competitive cover crops also reduce weed size and biomass when planted at the correct times.

Pest management system

Proctor discussed three main tools – herbicides, pesticides and cover crops – he feels an effective pest management system can include.

Producers are encouraged to not rely on herbicides to do all of the work when it comes to managing weeds. If herbicides are not used in the correct way, weeds can develop resistance, Proctor shares.

He views using cover crops as diversifying the overall management system – transferring some of the workload from the herbicides to the cover crops.

Proctor finds no-tillage fields benefit greatly from using cover crops to manage weeds instead of increasing the use of herbicides. 

“Cover crops are a tool to play a role that tillage once played,” he says. 

Another advantage of planting cover crops is the ability to minimize reliance on pesticides. Different cover crop species can attract beneficial or predatory insects.

Increasing these insect populations can have a positive impact on insects which typically act as pests and negatively affect cash crops.

“Usually, we see a greater diversity of insects in fields that are growing cover crops than those without,” Proctor explains. “Having a broader diversity of insects present tends to be beneficial to the system as a whole.”

Financial benefits

Cover crops may also offer growers a financial benefit by decreasing the cost of herbicides and pesticides each year. Proctor says he’s not yet seen cover crops used instead of herbicides, but  it’s what growers are “striving towards.”

Proctor says a major goal of growers is identifying the economic value cover crops are providing and identifying how much weed suppression they are getting from cover crops.

More and more growers are interested in interseeding cover crops into cash crops. For example, interseeding a cover crop into corn early in the growing season, preferably during week three or four, may offer enough weed suppression benefits to last into the season, he explains.

This practice can potentially limit a herbicide program, he says.

Proctor is interested in finding out if producers can successfully manage continuously growing cover crops throughout the season. 

In this scenario, when one cover crop is terminated, a cash crop is planted and a cover crop is planted right into the cash crop to “keep the cycle going.”

“I think the closer we can get to this ideal, the more success we might see in being able to start minimizing the herbicides used. It’s not the tool to straight replace herbicides yet,” he says.

Species selection

Proctor encourages producers to find out how cover crops can fit into their system and help meet their goals. There isn’t one cover crop species best for all growers to reduce disease and weeds, he shares.

“Species selection depends a lot on your goal and what the windows of opportunity are within your system,” Proctor says. “Diversity tends to improve resilience and our ability for our system to be managed through different environmental conditions.” 

He finds traditional cropping systems with a short window between harvest and planting, such as corn and soybeans, benefit from planting winter cereal grains as cover crops.

Cropping systems with a larger window between harvesting and planting, such as wheat, offer more time for growers to establish a whole range of cover crops, including opportunities for interseeding and establishing more diverse mixes, he explains.

“I think there’s value in these diverse mixes if you allow yourself enough opportunity for these mixes to establish, grow and produce biomass,” he says. “If we don’t have enough seasons for those mixes to grow, they tend to be more expensive and your money is better spent focusing on one or two species you know will be successful rather than trying to push a mix that might not be successful.”

He encourages producers to think about their individual systems and the goals they’re trying to achieve. 

Proctor says new growers should start small and work their way up, figuring out what works and how to be successful. 

“It’s a little bit of trial and error for each field and each grower. Considering it a one size fits all just wouldn’t be true,” Proctor concludes. 

Kaitlyn Root is an editor for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.