By STEVE BROWN
Seeding summer annuals in the pasture can benefit dairy farmers, an agronomist says.
The annuals tolerate drought, fill feed gaps during the summer, add biomass to the crop, fit well into crop rotations and can be used for grazing, silage or grain.
Heather Darby, an agronomist at University of Vermont Extension and co-owner of an organic farm, described research she has led comparing different kinds of annuals. A $2.8 million grant from USDA's National Institute of Food and Agriculture involved 14 farms and four research facilities.
Joining her in a recent webinar was Rick Kersbergen, professor at the University of Maine Cooperative Extension, who said summer annuals provide diversity, or "insurance," for changing climate conditions.
"Because ruminants are designed to eat forage, pastured forage is the cheapest source of digestible nutrients," he said.
They described several annuals:
* Sudangrass has a fine stem and is leafy, with good regrowth. It's best to graze at 18 to 30 inches tall, and graze down to 6 to 8 inches. Sudangrass provides two or three grazings, and Darby recommended clipping the pastures after grazing for better regrowth.
* Sorghum is a one-cut system, with lower regrowth and thicker stems. Its best use is baleage or silage, harvesting at 36 to 48 inches, cutting to a height of about 6 inches. It can be difficult to dry, but it yields 6,000 to 7,000 pounds of dry matter per acre with good quality.
* Sorghum x sudangrass combines the best traits of both, with moderate regrowth.
* Pearl millet and Japanese millet are bushier, tolerate both drought and wetter conditions, and have smaller stems with greater leaf biomass. When the crop is 12 inches tall, graze it down to 6 inches, Darby said. She recommended letting the millet head out after one grazing to save seed for the next season. Kersbergen said some millets contain the BMR gene (for vigor) and are higher in crude protein than sorghum x sudangrass.
* Teff has fine stems, is leafy, drought-tolerant, has rapid growth and is best for hay harvest. Both teff and millet can be stored as baleage or silage, harvesting at 36 inches and cutting to 5 to 8 inches. Millets yield about a ton less per acre, but are higher quality with higher protein and total digestible nutrients.
* Corn is good for grazing, silage and baleage, but provides only one harvest, no regrowth and is not as drought-tolerant as other annuals. "It didn't seem to work out for us," Darby said, suggesting it may work better as a cover crop.
She suggested planting at a soil temperature of 60 to 65 degrees, using a grain drill at 1 to 1.5 inch depth. Planting in early June to early July will mean reduced weeds but less production.
Teff is a small seed, and seeding 4 to 5 pounds per acre works well. Millet is 28 to 30 pounds, and sorghum, sudangrass and sorghum x sudangrass are 35 to 55 pounds. Successional planting works well with grazing systems to keep the forage at proper grazing height, Darby said.
The practices adapt well to small-scale operations, Kersbergen said, but staggered plantings are even more important.
He said summer annuals are good weed-controlling cover crops for vegetable producers, and Darby recommended double-crop systems, growing winter grains, grazing in spring, then reseeding summer annuals.