NORTH AMERICAN
MANURE EXPO 2017 AUG. 22-23 • ARLINGTON, WISCONSIN
Consider cover-crop wins, losses JANE FYKSEN
jfyksen@madison.com 715-683-2779
MADISON, Wis. — Consider wins and losses with fall-applied manure and cover crops. That’s the question University of Wisconsin-Madison soil scientist Matt Ruark is attempting to answer with a three-year study at three locations in Wisconsin. Matt Ruark With more than 1 million acres of corn silage grown in Wisconsin and harvested in late summer, there’s a clear opportunity for cover crops to be planted to hold soil through fall and early spring. In addition, cover crops provide nutrient-conservation benefits if manure is applied after the corn silage comes off. Cover crops work with fall manure applications to immobilize manure nutrients until the following spring. “(But) this soil-health-promoting practice is not without potential tradeoffs, including yield drag and increased (nitrogen) demand,” Ruark said. He said while corn silage, fall-applied manure and cover-crop seeding is growing in popularity, growers have concerns about trade-offs with cover crops. There is extra cost and field work in the spring, and covercrop competition for nutrients and soil moisture. The potential for yield loss in the following year’s corn is also a real concern. Ruark is in the final year of a three-year study to determine performance of fallseeded cover crops in a production system with corn silage and fall-applied manure. He’s quantifying the effects on corn yield and optimal nitrogen rate in the subsequent corn crop. He evaluated winter rye
Winter rye produces a relatively large amount of spring biomass, as shown in 2016 at the University of Wisconsin-Arlington Agricultural Research Station. Preliminary research results suggest optimum nitrogen rates for corn might need to be tweaked when cover crops are grown.
CONTRIBUTED PHOTOS
Spring barley is a fall-planted cover crop after corn silage and fall-applied manure that winterkills, leaving behind little dead biomass in the spring.
– which requires termination in spring with a pesticide – and spring barley, which growers a little faster in the fall but winter-kills. The study was conducted in 2015 and 2016 at the UWAgricultural Research stations in Wisconsin near Lancaster, Arlington and Marshfield. When corn silage was harvested, a target rate of 10,000 gallons per acre of liquid dairy manure was applied. First-year available nitrogen from manure was about 100 pounds per acre at Lancaster and Arlington. At Marshfield,
low-percent solids in the manure resulted in a much lower nutrition contribution. A f te r t h e m a n u re wa s injected, the cover crops were drilled at target rates of 90 pounds of pure live seed per acre of winter rye and 80 pounds of spring barley. Cover crops were planted mid-September, as recommended. The following spring, no-till corn was planted and variable rates of nitrogen applied – 0, 50, 100, 150, 200 and 250 pounds per acre. The nitrogen was broadcast as urea with Agrotain.
After two years, Ruark found: • D ry-matter cover-crop yield of winter rye was at least 0.5 ton per acre at all locations, with all locations in 2016 having greater than a ton of dry-matter biomass per acre in the spring. Ruark said a ton of spring biomass is too much. He’d prefer to see 0.5 ton or less. • A t Arlington and Lancaster, winter rye always reduced soil nitrate in the upper inch in the fall compared to no cover. The effect was less pronounced at Marshfield. • A veraged across six site-years, a winter-rye cover crop resulted in a 16-bushelsper-acre yield drag. Corn-grain yields after spring barley were, on average, 7 bushels per acre less. • O n average, corn following winter rye required 35 pounds more nitrogen per acre for the corn to achieve the yields it did, See CROP, Page 5