Manure-slurry seeding of cover crops produces an excellent stand and saves time and money, a Michigan State University expert says.

No-tillers who must apply manure late in the summer and also want to drill cover crops face a conflict. When storage nears capacity, manure must be applied to fields. But timely seeding of cover crops is crucial to establishing stands.

SLURRY SEEDING. Despite being told manure and cover crops can’t be used together, Michigan State University field trials have shown that it’s not only possible, but the system can yield good results.

“We were always told that you couldn’t put manure and cover-crop seeds together because they wouldn’t grow or wouldn’t germinate,” says Dale Mutch, cover-crop specialist.

But research at Michigan State University proved seeding cover crops with liquid manure can work, says Mutch, who has been studying this practice for 7 years.

“Cover crops provide clear benefits to no-tillers,” says Mutch, who spoke at last year’s National No-Tillage Conference in Des Moines. “We’re going to increase water-holding capacity, improve aggregate stability and water infiltration, decrease evaporation and improve soil bulk density.”

Slurry And Drilled

One study with cover crops in manure slurry compared the establishment and biomass yield of oilseed radishes and Oriental mustard. This study was done during the hot, dry summer of 2005 that stressed crops, Mutch says.

Researchers seeded cover crops into winter-wheat stubble.

They attached an AerWay rolling-tine aerator on the rear of a liquid-manure tanker. The aerator poked holes 1/2 to 1 inch deep in the ground. The slurry with the seeds traveled through a rotating chopper-distributor and drop tubes and then into soil fractured by the rotating tines.

Manure slurry containing cover-crop seeds filled these holes. The study compared this method to no-till drilling cover-crop seed into the same harvested wheat field.

“Using the AerWay slurry system offers no-tillers two main benefits,” Mutch says. “They gain efficiency by combining manure application and cover-crop seeding in one trip, and the AerWay minimally disturbs the soil.

“The AerWay system is approved by the state of Michigan, which requires that liquid manure applied to fields be incorporated.”

In the study, the seeds germinated, established a good root system and grew out of the holes that the AerWay machine made.

Five Cover Crops

In another study, Mutch used five cover crops. Seeds were no-tilled with and without manure and compared to tests of the four cover-crop seeds with the AerWay and manure slurry.

Tim Harrigan, Michigan State University biosystems and ag engineer, no-till-drilled annual ryegrass at 35 pounds per acre, cereal rye at 2 bushels per acre, crimson clover at 15 pounds per acre, oilseed radish at 15 pounds per acre and Oriental mustard at 10 pounds per acre.

These treatments were compared to a control where no cover crops were seeded. This study also was done during the hot, dry summer of 2005.

“Cover crops seeded with the manure slurry benefited from that moisture,” Mutch says.

Researchers found 35 mustard plants in 3 linear feet in the no-till-drilled area, but just 10 mustard plants in the manure slurry treatment.

"We were always told that you couldn't put manure and cover-crop seeds together..."

— Dale Mulch

“However, the 10 plants were bigger and sturdier than the 35 plants in the no-till-drilled area,” Mutch says. “The oilseed radish that was no-tilled was stressed, but the radishes in the manure slurry looked healthy because of the moisture in the manure slurry.

“This was also the case for annual ryegrass that was seeded in manure slurry. The plants were greener and had more top growth than the no-till-drilled treatments. But overall, both cover-crop treatments ended up having the same amount of biomass.”

The no-till-drilled cover crops and those seeded in manure slurry provided excellent cover, Mutch says. The hot weather and early seeding in 2005 stressed the cereal rye, he says, noting that cereal rye typically is not seeded in August.

Mutch offers a caution to no-tillers considering mustard as cover crops.

“Don’t let it go from being beneficial to a weed,” he says. “As a biofumigant for controlling disease, mustards do well. But because they produce many tiny seeds, they should be controlled soon after flowering.”

There were some surprising results with crimson clover, he says. The no-till-drilled crimson clover without manure looked very good, but seeding crimson clover in manure slurry did not work.

Chickweed emerged instead of crimson clover, Mutch says. Chickweed would work well as a cover crop, but could increase problems with black cutworms, he says.

Nitrogen Credit

Researchers fertilized the plots with a yield goal of 120 bushels of corn per acre the following year. If cover crops gave them 50 pounds of nitrogen, they applied 70 pounds of nitrogen.

HOLES HELP. Rotating tines from an AerWay aerator attached to a manure tanker poked holes 1⁄2 to 1 inch deep, which the manure slurry filled and from which the cover crops emerged.

“When we used manure, we had very good yields for this type of sandy soil,” Mutch says. “Where we didn’t use manure, we had pretty good yields.”

Researchers used the pre-sidedress test for soil nitrate (PSNT) and found that crimson clover provided a nitrogen credit of 105 pounds per acre.

“But that didn’t turn out to actually be the case,” Mutch says. “You’ve got to be careful about these PSNT tests. They’re not perfectly accurate.”

Overall, Mutch says cover crops and manure can provide no-tillers concrete benefits.

“Where we used the manure, we had really good results and good cover crops,” Mutch says. “Including manure and cover crops in the cropping system can improve yield, soil quality and crop health.

“Manure is going to help you build organic matter, at least in the top surface.”

Mutch offers two cautions for no-tillers who try the slurry seeding method for cover crops. Pulling a slurry tank requires a tractor with more horsepower than needed for a no-till drill, he says.

And while slurry seeding with the low-disturbance Aerway worked in sandy-loam soil, it might not work in every situation.

“We heard from a farmer who said on his heavier clay that the AerWay is not really a great tool,” he says. “You have to listen to the farmers with experience.”