Soil and water conservation leaders in Allamakee County in far northeast Iowa are working with local livestock producers to find the best methods for growing cover crops and using manure fertilizer on crop fields, while minimally disturbing the soil with no-till.

LuAnn Rolling, district conservationist for USDA’s Natural Resources Conservation Service in Allamakee County, says one of the challenges for cover crop implementation is overcoming the mindset that cover crops cannot be used on acres with applied manure — because manure drowns the seed or the timing of the manure application.

Allamakee ranks in the top five Iowa counties for number of dairy cows, and is in the top 10 for number of beef cows. “Manure is a natural fertilizer source we encourage farmers to utilize on ag lands,” Rolling says. “Manure helps increase organic matter in soil, and it has significant energy savings.”

Rolling says cover crops provide water quality benefits when used in conjunction with manure. “Cover crops can scavenge nutrients and provide cover and ground surface protection during the fall and early spring when warm-season crops like corn and soybeans are not growing,” she says.

Allamakee Soil and Water Conservation District (SWCD) project coordinator Sara Berges is working with a handful of farmers on a project funded through the Leopold Center for Sustainable Agriculture to find what method, timing and cover crop species work best.

“We want to see as much cover crop growth in the fall as possible,” Berges says, “and we want farmers to use a winter-hardy cover crop like cereal rye that will survive and continue to provide benefits in spring before planting.”

Several Allamakee County farmers worked with Berges and the local NRCS office to plant cover crops in conjunction with injecting manure.

4 seeding methods tested
Ross Weymiller farms with his father, David, and his brother, Frank. They have a 6,100-head hog operation and farm about 1,200 cropland acres near New Albin. They chopped silage the first week of September, and planted cover crops on portions of their rich, sandy, river-bottom ground to help improve soil health. They also planted a few acres on their highly erosive ridges. Weymiller used the following four methods of cover crop planting with manure injection on 5- to 20-acre plots, totaling 40 acres:

• drilled in cereal rye seed and then injected manure

• injected manure and then drilled in cereal rye seed

• injected manure, vertical-tilled and then drilled cereal rye seed

• mixed cereal rye seed with liquid manure, and injected manure and seed together.

Of the four methods, only the manure and seed mix resulted in a substandard cover crop stand. “The seeds either floated to the top and came out first, or sunk to the bottom of the tank and came out last,” Weymiller says. “The manure-seed mix would work if you could somehow disperse the seed equally inside the tank.”

In summarizing his cover crop and manure trial, Weymiller says:

• It was easiest and most timely to drill the rye seed into the ground, right behind the manure injection.

• There was no need for tillage, especially because there is little crop residue after chopping silage.

• Injecting manure into a growing cover crop temporarily tears up the stand. However, in his experience, Weymiller says winter-hardy cover crops like cereal rye come back fine in the spring.

Overcoming cover crop challenges
Scott Ness keeps busy on his Waterville farm with a 185-head ewe-to-lamb operation, feeding about 8,000 nursery pigs and growing 190 acres of crops. Ness, who won Allamakee SWCD Cover Crop Grower of the Year in 2016, has been using cover crops to reduce erosion and improve soil health for seven years.

Ness is a longtime no-tiller who says he will inject manure on every cropland acre in 2018, thanks to available manure from his growing hog operation. And many of those acres will be a sea of green cover crops.

In 2016, Ness purchased a 15-foot Case IH grain drill to improve cover crop planting efficiency. “The few times we aerial-applied cover crops, we didn’t get a very even stand,” he says. “We’ve tried several planting methods and cover crop mixes. We can get cereal rye to grow consistently well. We have great results when Mother Nature cooperates with us.”

Earlier-maturing soybeans help
In 2017, Ness drilled cereal rye and Austrian winter peas into harvested soybean stubble in late October. By the end of November, the cover crops started to green up. A month later, he knifed manure into his green cover crop. “We’ve actually started to grow early-maturity soybeans to get them out of the ground sooner,” Ness says. “We get the same yields as the late-maturity. We plant the beans in late April before corn. It works!”

Growing cover crops is a challenge, but Ness feels the positives outweigh the negatives. “We factor in a certain amount of nitrogen from this cover crop,” he says. “Our tougher ground has become more mellow, and all of our soils are much easier to plant into now.”

In spring 2017, Ness missed an entire acre when terminating his cover crops with glyphosate. The rye grew to about 32 inches by the time he planted his corn. “I went ahead and planted into it,” he says. “I went back in and sprayed it, riding on my ATV. We did a yield check on that acre, and it yielded 41 bushels better than what we yielded 90 feet away where we terminated early,” Ness says. He is going to purposely plant into green cover on a larger area this spring. “I won’t let it grow to 32 inches, but I want to see if I get the same kind of yield bump,” he says.

Manure, timing make a difference
Matt Byrnes of Dorchester has been milking dairy cows for nearly 20 years. With 180 cows, he pumps manure from a pit about twice per year, and either knifes or top-dresses it to as many of his 484 cropland acres as he can.

Byrnes tried cover crops on a few acres once before, but late September was the first time he gave it a “good effort” when he broadcast cereal rye on 30 acres of chopped silage in combination with pelletized lime. The custom applicator pumped the manure pit and top-dressed the cover crop two days after cover crop application. “Luckily, we caught a rain a few days after that,” he notes.

Two months after application, Byrnes observed that he didn’t have a perfect cover crop stand, but it looked much better than it did a month prior. “There are some areas where the manure was a little thick, and the cover crop had trouble coming up through that,” he says. “Driving over to spread manure packs it in and causes cover crop growth issues, too.”

As a dairy producer, Byrnes says the manure doesn’t have the same consistency as hog manure, which makes growing cover crops in conjunction with manure application a little more challenging. In areas where the manure was more watered down, the cover crops responded better. He hopes the cover crops help reduce soil compaction, improve water infiltration and add to the biology in the soil. “When I chop silage, I’m taking a lot off, so cover crops help with organic matter, too.”

Project to fund additional trials
The NRCS offices in Clayton and Allamakee counties are looking for producers like Weymiller, Ness and Byrnes who are interested in planting cover crops in conjunction with their manure application.

Allamakee SWCD and four conservation partners were recently awarded funding from USDA through the Innovative Conservation Agriculture Project to provide financial and planning assistance to producers in Allamakee or Clayton county to support the implementation of cover crops and no-till in conjunction with manure application. Through this Regional Conservation Partnership Project, farmers can receive up to $6,000 per contract for cover crops and up to $1,500 per contract for no-till.

For information about cover crops and no-till with manure application, visit your local NRCS office.

Johnson is a public affairs specialist with NRCS in Des Moines.