Manure and cover crops are a natural combination, but livestock farmers are often too busy in the fall with harvesting and manure application to worry about putting in a cover crop.
Now, a new seeding technique makes it more practical for Midwest growers to reap the benefits of cover crops without an extra field pass. Slurry seeding combines liquid manure injection, low-disturbance tillage and cover-crop planting – all in one efficient operation.
The new method works especially well in no-till or reduced-tillage cropping systems, which often have a hard time making use of manure, says Tim Harrigan, a Michigan State University (MSU) Extension ag engineer. Growers who take advantage of the synergy between manure and cover crops will improve their soil quality, reduce nutrient losses and erosion, suppress winter annual weeds and add value to manure, Harrigan says. “Cover crops and manure together create a synergy that’s better than manure alone and better than cover crops alone.”
Here’s how slurry seeding works:
Cover-crop seed is mixed directly with liquid manure in a commercial manure tanker. Bypass flow from the PTO pump agitates the manure and keeps the seed suspended in the slurry. An aeration tillage tool with rolling tines is pulled behind the tanker to loosen and fracture the soil. The manure-seed mixture flows through drop tubes behind the aeration tines and is deposited in soil cracks. There’s no other tillage.
“Manure carries the seed into the soil fissures and gives it a quick start,” Harrigan says. In turn, the growing plants capture manure nutrients, hold the soil in place over the winter, improve water infiltration and soil structure and reduce manure runoff, he says. Next spring, the nutrients are available for the cash crop.
The three-in-one operation also cuts fuel use by about 2 gal./acre and labor by a good 30 minutes/acre, Harrigan says. “We see a lot of opportunity for this seeding method.”
Slurry seeding works well for a variety of cover crops, such as wheat, cereal rye, annual ryegrass, forage clovers and late-season grazing crops like oilseed radish and forage turnip. In northern regions, slurry seeding is ideal for cover crops planted in early August after wheat harvest, but it also works after harvesting corn silage, seed corn, vegetables or even early maturity soybeans.
Ken Blight and his brother Art grow corn, soybeans and wheat and raise hogs and cattle at Albion, MI. They’ve been no-tillers since 1990. Eliminating tillage has helped the Blights build up their soil organic matter, conserve moisture, reduce erosion and hold down the number of rocks surfacing in their fields.
The Blights have long seeded clover after spring wheat, but their stands were often spotty, “so we couldn’t get a consistent nitrogen credit,” Ken Blight says. When MSU asked for farmers who wanted to experiment with slurry seeding cover crops, the Blights jumped at the chance.
For the past two years, they have worked with Harrigan to slurry seed oilseed radish or a mixture of oats and forage turnips in early August on a 40-acre harvested wheat field.
By September, the slurry-seeded fields “had beautiful growth,” Blight says. But the same cover crops planted without manure were “more anemic,” he says, “and we didn’t get nearly the benefits. It’s the combination with manure that really makes this shine.”
The vigorous crop cover also smothered winter annual weeds and volunteer wheat, Blight says. Normally, he fights purple henbit, chickweed and pokeweed, but “when I went to spray a burndown this spring, there was nothing there.”