Choose the right cover crops

THERE’S NO QUESTION that today’s farmers are innovative, adaptable, and always looking for new techniques and technologies to improve their farming practices. A trend that is gaining more ground is the use of cover crops, and planting cover crops into corn and soybeans. Including cover crops into a rotation can have a number of agronomic and economic benefits.

Cover crops can reduce erosion, improve soil structure and health, and promote greater biodiversity. Depending on the cover crop used, this living ground cover can bank or even produce nitrogen. They incorporate well, especially after wheat, and in conventional and no-till systems while also adding an extra revenue stream to the farming operation.

Despite the wealth of benefits that cover crops can bring to the field, a cover crop’s success is dependent on matching the right crop (or mix of crops) for the goal and managing it properly.

“Cover cropping isn’t a science, it’s an art,” says Warren Schneckenburger, from Morrisburg, ON, (District 14). “There definitely is science involved, but really making it work on your own farm takes some outside-the-box thinking.”

Schneckenburger says that a cover crop strategy needs to be goal based, with long term results in mind, even though those results can sometimes be challenging to quantify. “There isn’t really one right answer, in my opinion, and what works for your neighbour might not work for you,” he says.

ONLINE SELECTION TOOL
That’s why the Cover Crop Decision Tool was developed. Based on a tool previously created for field crops by the U.S. Midwest Cover Crops Council, this new tool was developed for Eastern Canada as a resource for growers to help select the cover crops that would best fit their needs and goals.

According to Dr. Laura Van Eerd, associate professor, School of Environmental Sciences, University of Guelph-Ridgetown, who lead a team of cover crop experts that helped gather information for the Ontario tool, the approach was to first create a comprehensive database of potential cover crop species and mixtures which would be suitable to grow in each province.

“The database was created by engaging a team of cover crop experts from diverse backgrounds, including researchers, growers, industry representatives, and government specialists, and involving them directly in data assembly and verification,” says Van Eerd. “Project teams in each of the five target provinces (Ontario, Quebec, Nova Scotia, New Brunswick, Prince Edward Island) ensured that only regionally appropriate information was included in the database.”

COUNTY-LEVEL PRECISION
In addition to the wealth of knowledge provided by industry experts, climatologists analyzed weather data from a number of locations in the province to establish reliable planting dates for cover crops based on location down to the county level. Information pertaining to cover crops, such as agronomic practices, potential benefits, and limitations was gathered from public scientific information, research results, and on-farm experience. The information was reviewed by the team to ensure accuracy before being added to the tool.

“The tool is designed to assist farmers and other working in the industry in selecting cover crops for field crop rotations based on their soil type, risk of frost, and objectives,” says Van Eerd. “Goals could be fighting weeds, building nitrogen, controlling erosion… cover crops can help with all of these problems but no one cover crop can do it all. Therefore, you want to pick the right cover crop to meet your needs. So far, the feedback has been very positive, especially about the amount of information available.”

MAKING IT WORK
In the tool, each cover crop has a profile, specific to Ontario conditions and management systems. The profile gives cover crop management information such as seeding rate and also outlines potential benefits and limitations, so growers can make informed decisions based on their operation.

Schneckenburger says he has used the Midwest Cover Crop Council Cover Crop Decision Tool to help determine which species were the best fit for his situation.

“Farming in Eastern Ontario presents many challenges for implementing cover crops into the tighter crop rotation,” he says. “Wheat is a challenging third crop because of severe fusarium pressure along the St. Lawrence and most farms grow only what is necessary for straw bedding.  The tool does show you what can be planted after the harvest window but that is minimal in many counties, especially after corn. After cereals or even early corn silage the tool is of use. The earlier harvest date really opens up the options the tool will suggest and you can get much more value from its guidance.”

However, Schneckenburger has noticed a few shortcomings from the tool as well.

“If you use the tool and enter a typical corn or soybean crop with an early May planting date and a late October harvest date, effectively all the cover crop options are eliminated, but this doesn’t mean you can’t make it work. On our farm we chose winter cereal rye as our main type of cover and have been inter-seeding the rye into corn in early September to get it established and growing well before the end of October harvest date. This isn’t an option for the tool and thus it wouldn’t recommend cereal rye in a corn situation even though it fits my needs and goals perfectly.”

Schneckenburger also noted the tool doesn’t take into account herbicide carryover. “Seed is expensive and if it never even gets a chance because a herbicide sprayed months ago holds it back a farmer might be quite discouraged and get a ‘it doesn’t work here’ mentality,” he says.

Van Eerd agrees, “There are not a lot of cover crop options before or after corn and soybeans and the tool points this out. So many growers are interseeding cover crops into standing corn or soybeans. At the time of development over four years ago, we just didn’t have enough information on interseeding (into corn and soy) or herbicide residues. The great news is that Drs. Darren Robinson and David Hooker at the University of Guelph-Ridgetown are doing this research. With enough information, we can add it to the decision tool.” (See below).

The Cover Crop Decision Tool for Eastern Canada is available online at http://decision-tool.incovercrops.ca/.

HERBICIDE INJURY AND COVER CROPS
Dr. Darren Robinson, associate professor, University of Guelph-Ridgetown, has been studying incorporating cover crops into corn and soy rotations, as well as researching herbicide injury to cover crops.

Twelve field experiments were completed over a two-year period from 2014 to 2015 to determine the effect of herbicides in soybean and wheat on cover crop establishment. In four of the studies, 12 different pre-emergence herbicides were applied at soybean planting in May of both years. Oilseed radish was broadcast into standing soybeans at leaf drop of the soybeans, and monitored for injury, stand count, and yield. Though some herbicides caused visible injury symptoms to oilseed radish, there was no reduction in oilseed radish stand counts or biomass production.

In another four studies, seven different post-emergence herbicides were applied to soybean in June of 2014 and 2015 and oilseed radish was broadcast into standing soybeans at leaf drop. Pursuit reduced oilseed radish above ground biomass.

In the remaining four studies, ten different post-emergence herbicides were applied to winter wheat in the spring, and oilseed radish was planted after wheat harvest. None of the herbicide treatments injured oilseed radish.

Two field studies determined the establishment of annual ryegrass in corn. Annual ryegrass can be successfully established in grain corn at the three- and five-leaf stage of corn, but later planting timings (ie. seven-leaf and later) did not allow for successful establishment of annual ryegrass in corn. Other pre-plant corn herbicidecover crop combinations that are compatible for growers looking to interseed annual ryegrass into corn at the 5-leaf stage include using Converge XT, Engarde, and Prowl H2O. •