Terminating a cover crop isn’t just about applying Roundup and being done with it.
“It’s really not that easy because there are a whole lot of decisions you make up to that termination process,” says Eric Rosenbaum, a certified crop advisor and owner of Rosetree Consulting LLC. “You’re making decisions the whole way through, from the decision to plant the cover crop, what kind of plant you use, the seeding methods, there are a million decisions that go into it.”
Rosenbaum, who spoke at a recent no-till conference in New Jersey, says he focuses on four things — increased production, reduced production costs, better efficiency and improved sustainability — when advising farmers on what cover crops to use.
“If you can find a practice that is going to do two of those things, then it’s a practice that you can bring on your farm and keep on your farm for a few years to try it out,” he says.
A long process
Some cover crop practices won’t work while others might take a few years to be successful.
Rosenbaum says it’s all about what the end goal is.
“If you’re going to plant a cover in September and no-till in May, think about the obstacles and hurdles with this in addition to thinking about establishment,” he says.
His own experience with cover crops goes back to when he farmed his family’s dairy in southeast Pennsylvania. From 1999 to 2008, he and his family grew 50% corn silage and 50% alfalfa on the farm. After 2008, when the cows were sold, they went continuous corn for eight years straight.
They got decent yields, he says, but his soil organic matter lagged, growing a paltry one half of 1% through 2016.
Rosenbaum says cover crops were a good solution to help solve his farm’s yield and sustainability goals, but it always comes down to overall farm profitability.
“We can’t be spending $30 on a cover crop in order to get $15 in return,” he says. “You can get cover and no-till to get you more profits, but it will take tinkering and time to do it, to figure out the scenarios that are most efficient.”
Different termination methods
Every farmer has a different goal, even when it comes to terminating cover crops.
“If you’re wanting to increase carbon matter, you don’t want to eliminate that cover at 6 inches tall. If your goal is nitrogen, you don’t want to eliminate it April 1 because you probably won’t get much nitrogen out of it. We have to keep in mind our goal when we're thinking about termination of our crops.”
Termination comes in many forms, whether it’s planting a cover crop to winter-kill, tilling it down in spring or harvesting it as a forage.
Certain cover crops will need extra management. Rye, for example, can grow again after being harvested, so you might want to terminate it with an herbicide or something else.
If you’re burning down a cover crop, Rosenbaum says to remember that you’ll be spraying when it’s cooler and when crops are growing, so double-check your water source.
If using glyphosate, keep in mind that it doesn’t do well when daytime temperatures are less than 50 degrees F and nighttime temperatures are less than 30 degrees. Also, always use water with glyphosate and make sure nozzles and pressure are good. Between 32 and 44 ounces are needed for winter annuals depending on how high they get. Rosenbaum says atrazine can enhance Roundup on cereal grains.
When it comes to annual ryegrass, he says farmers should get to it before it joints as it can become a weed very quickly. The challenge, he says, is that spraying it young may not coincide with your other cover crop goals. “So be very careful with annual ryegrass. You may have to lower your rate of glyphosate. You may have to rely on two passes in order to get a complete kill.”
For broadleafs, including crimson clover and legumes, a tank mix of 2,4-D and dicamba will do the trick, but watch out for restrictions, especially when it comes to dicamba.