Manure application coupled with cover crops works

2012-06-13T14:51:00Z Manure application coupled with cover crops worksBY JANE FYKSEN, CROPS EDITOR Agri-View
June 13, 2012 2:51 pm  • 

Producers have a new, cost-effective and resource-efficient option to improve coil quality – not to mention an environmentally sensitive way to use manure in no-till and diverse cropping systems. It’s manure slurry seeding of cover crops, which is being promoted by Michigan State University, which has pioneered the practice.

In one pass, cover crop seed that’s been mixed with liquid manure in the spreader tank is delivered through drop-tubes to fractured and loosened soil behind aeration tines. A cover crop soon emerges, capturing nutrients and forming a vegetative barrier to overland flow.

The process has been in development at MSU since 2003. As noted, cover crop seed is mixed with manure in a slurry tanker equipped with a rear-mounted rolling-tine aerator. Seed-laden slurry is then passed through a hydraulically driven, rotating chopper/distributor. No additional seedbed tillage or soil firming is required. Manure slurry-enriched seeding of cover crops builds soil quality by reducing tillage intensity and adding organic matter. The process can also help crop producers save fuel, expand land base and windows of opportunity for manure spreading. And it protects water quality by preventing runoff, erosion and sedimentation of waterways and streams. MSU ag engineer Tim Harrigan has been at the forefront of slurry seeding. (Producers can contact him at 517-353-0767 or

According to Harrigan, more intensive cropping has led to yield declines and compacted and poor quality soil. Cover crops in the Brassica (mustard) family offer benefits in soil conservation, improved soil quality, less nitrate leaching, even suppression of certain pests and soil borne fungal diseases. He says establishing cover crops conventionally after harvest can be a challenge as soil is generally dry, compacted, uneven and “far from an ideal environment” for seed germination. The bottom line on MSU’s work: Biomass above ground and total from manure slurry seeding plants was significantly greater in two of seven comparisons and in no instances did conventionally seeded crops yield significantly more. Seed size of the cover crops researched weren’t a factor in slurry seeding success either.

Harrigan reports that nutrient-rich, seed-laden slurry quickly infiltrates soil, minimizing nitrogen losses. The loose soil surface prevents erosion and phosphorus runoff. A cover crop soon emerges, capturing nutrients and forming a vegetative barrier to overland flow. The aerated soil resettles and is generally suitable for no-till planting with no additional seedbed tillage. Manure is retained in the root zone for nutrient cycling.

He reports from several years of research that biomass yields of oil seed radish, oriental mustard, annual ryegrass, cereal rye, oats, wheat, forage rape, and forage turnips sown in untilled wheat and corn silage stubble with swine, dairy, and beef slurries were equal to or greater than a conventional seeding.

Unlike conventional planters and drills that open a seed furrow, put seed at uniform depth, and then firm it up, manure slurry seeding mimics nature’s way of seeding, where seed drops to the ground from seed pods or in animal manure or bird feces and infiltrates by water into soil cracks to germinate. Manure slurry seeding relies on aeration tillage to make fissures which are then infiltrated with nutrient-rich seed-laden slurry – without additional seedbed tillage, according to Harrigan.

MSU does its slurry seeding with a commercial tanker equipped with a rear-mounted rolling-tine aerator (an AerWay) and a sub-surface deposition slurry system (SSD). The aerator is ground driven with sets of four eight-inch tines spaced at 7 1/2 inches between sets. The gang angle can be adjusted. Cover crop seed is mixed with manure in the tank and passes through a hydraulic rotating distributor and through drop tubes to fractured and loosened soil behind each set of rolling tines.

Although MSU’s work has been primarily with cover crops, they let some winter wheat and cereal rye test plots seeded after corn silage to go to grain to measure yield and found no significant difference in grain yield between winter wheat slurry seeded with 5,000 gallons per acre of dairy manure and drilled wheat with 50 pounds of commercial nitrogen in the spring. The wheat yielded 75 to 80 bushels, the cereal rye 65 to 70 bushels.

They compared commercial variety of winter wheat (Vinson) and a common variety of cereal rye established in late September in corn silage stubble. Specific treatments were: Surface manure, no tillage, no seed; wheat, 2 bushels per acre, no-till drill, 50 pounds of N; wheat, 2 bushels, slurry seed, 5 percent gang angle; wheat, 2 bushels, slurry seed, 10 percent gang angle; wheat, 4 bushels, slurry seed, 5 percent gang angle; wheat, 4 bushels, slurry seed, 10 percent gang angle; cereal rye, 2 bushels, 5 percent gang angle; and cereal rye, 2 bushels, 10 percent gang angle.

The wheat was sown with a Great Plains no-till drill (Sept. 24) and both wheat and cereal rye were sown with a new manure slurry-enriched seeding process (Sept. 29). The seed-laden dairy slurry was applied at 5,000 gallons. The slurry (9.5 percent solids, sawdust bedding) provided 125 pounds per acre of total N, 43 pounds of phosphorus and 140 of potassium K.

“Manure slurry-enriched seeding of wheat and cereal rye cover crops in untilled corn silage stubble was an efficient and effective establishment method,” Harrigan states. “The cereal grain cover crops suppressed weed growth, and manure application did not increase weed competition in the subsequent cover crop.”

MSU has also explored slurry-seeding forages for late-season grazing. Forage rape (Barkant variety at 6 pounds per acre), forage turnip (Pasja variety, also at 6 pounds per acre), brown midrib sorghum-Sudangrass (Sudex variety at 30 pounds per acre) and common oats (at 64 pounds per acre) were sown in untilled wheat stubble on a sandy loam soil in August. Two seeding methods were compared: Conservation tillage with two passes of a combination tillage tool (12-foot Kongskilde Triple-K, 3-inch tillage depth) and slurry seeding with aeration tillage and seed-laden swine slurry (10-degree gang angle, 6,000 gallons per acre). Fifty pounds per acre of nitrogen (as urea) was applied to the tilled-and-drilled plots before tillage and planting. No commercial N was applied to the slurry-seeded plots. The Sudex and oats were harvested Oct. 21, the rape and turnip Oct. 27.

According to Harrigan, the weather was hot and dry in August. The tilled-and-drilled oat stand (43 plants per square foot) was significantly greater than the slurry-seeded stand (24 plants), but there was no difference between the tilled-and-drilled and slurry-seeded forage rape, forage turnip or Sudex stands. (Sudex did not establish well with either seeding method.)

Forage rape and forage turnip yielded better than sorghum-Sudangrass and oats, but there were no significant differences within a crop due to the seeding method. Harrigan concluded that slurry seeding of forage turnips, forage rape, oats and other forages in wheat stubble is an effective alternative for establishing late-season grazing crops to extend the grazing season.

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