STRENGTH IN NUMBERS: MIXING A COVER CROP COCKTAIL
Some folks spend their time dreaming of a nice, tall cocktail on a sunny beach somewhere. Larry Bonnell dreams up cocktail mixes for his 300-acre operation near Pittsford, Mich., but not the alcoholic kind – he’s blending cover crops.
In cooperation with the Great Lakes Cover Crop Initiative, an effort to promote and study cover crops in the Lake Michigan, Lake Erie and Lake Huron watersheds, Bonnell put out 40 cover crop test plots, testing two-way, three-way and even eight-way blends of various cover crop species. He’s watching carefully to see which ones seem to benefit his beloved “bugs” – the bacteria, fungi and actinomycetes in his healthy soils.
“The more diverse you can be, the better off you are,” Bonnell explains. “Different bugs like different things.
“I like four-, five- or six-way mixes,” he adds. “I like a grass and a legume together – everybody to feed one another. I always like an 18-pound mix. Nobody overwhelms anybody else. Everybody gets their share.”
Each plant in one of Bonnell’s cocktails also contributes its share. Legumes like clover, Austrian winter peas and sunn hemp fix nitrogen in the soil, fueling the cover crop and providing nutrients for the cash crops to follow. Grasses like annual ryegrass and oats reach deep into the soil to loosen hardpan and capture nitrogen, keeping the legumes’ contribution where cash crops can eventually use it. Root crops like tillage radish and turnips – and their tap-rooted brassica cousin, rapeseed – drill down through tight soils like shanks. Bonnell has also planted sorghum sudangrass, buckwheat, and even some of his wife’s millet birdseed.
“It’s a cover crop, not a beauty contest,” he jokes.
Pick Your Timing
The best mix for a particular site will depend on the soil, the goal, and the date of planting.
Warm-season cover crops like dwarf Essex rape, sunn hemp and tillage radish are great for seeding into wheat a few days before combining. Bonnell points out that in his area, on the Michigan/Ohio border, radishes can be touchy – they need to be planted early enough to bulk up their taproots before they succumb to frost. That makes him indignant.
“I believe in the end of July, after you combine your wheat, is the best time for planting radishes,” he says. “They say, ‘you can plant them ‘till the end of September.’ You should see those puny things! At $150 a bag, you want a big radish. If I plant that seed at the end of July or the beginning of August, I’ve got a huge tillage radish and it don’t want for nothing.”
He’s a big fan of annual ryegrass, which overwinters easily in Michigan and is a much smaller-statured grass than cereal rye. Despite its winter hardiness, Bonnell notes, annual ryegrass has to be planted early enough in the fall to build up some growth before winter sets in. August and September are fine in his area, he says, but by late October, it was too late to germinate some of the annual rye he’d planted on October 20.
“Annual ryegrass gets a bad rap around here,” Bonnell notes, pointing out that it has a reputation for being hard to kill. It’s not easy, he admits, but it’s worth the worry.
“I like it eight inches or less when I kill it,” he says. “I will use better than a quart of Roundup per acre and throw in 2,4-D. Just don’t put atrazine in there – that will just make it mad!
“I like to spray a couple of weeks before I put in corn,” Bonnell adds. “I like to see that I’m getting a total kill in my annual ryegrass.”
In one field, where late-planted annual ryegrass kicked into high gear after spring rains, Bonnell had to beat it down with his crow-foot cultipacker. The tactic worked, and the soybeans he’d drilled into the cover crop came up a few days later without a problem.
Fifteen years of no-till and cover crops have helped Bonnell more than double his soil organic matter.
“My organic matter went from 1.4 to over 3.0 now,” he reports. “One field is over 4. Without cover crops, I wouldn’t be able to do it. It seems when I plant annual ryegrass, tillage radish and a few other things, my organic matter goes up one-tenth or more every two or three years.”
Healthy soils really paid off in the drought of 2012, Bonnell says. Where drought-stricken local corn averaged 60 bushels per acre or less, Bonnell was able to harvest 140 bushels per acre. His top-yielding soybeans that year delivered 58 bushels per acre.
“With all that organic matter, my corn didn’t roll up all summer,” he notes. “The cover crops kept that moisture in the ground, and the corn roots could dig down two, three, four feet into the ground to get that moisture. If your corn doesn’t have to break through a hardpan – think about it.”
“Try a little bit at a time,” he suggests. “Branch out.”
Pay attention to how your cover crops – especially cocktails – perform over time. “Every 30 days, I will look at it,” Bonnell says of each of his trials. “I take pictures of all my cover crops, too. That way, I know what they’re like and what they’re doing.”
Cover crops aren’t rocket science, he emphasizes – they just need a little attention.
“If people would give cover crops half the chance they give row crops,” he says, “they’d do fine.”
Even birdseed works!
Bonnell says that covering the soil is the main goal, and even throwing out birdseed will work to keep the ground covered: