Producers interested in improving forage quality and pasture productivity should consider frost-seeding clovers into existing stands as an inexpensive option to reach their goals. This long-standing practice, which involves broadcasting seed onto the soil surface during freeze-thaw periods in winter, can improve poor-producing or grass-dominated pastures.
“Frost-seeding is fast and a lot less expensive than tilling into an existing stand,” said Marvin Hall, professor of forage management at Penn State University. “Not only do you help the grass plants by providing more nitrogen through nitrogen fixation, but forage protein levels get a slight boost, too, which in turn increases animal productivity.”
Forage quality of most grass pastures averages somewhere between 15 to 20 percent crude protein, explained Hall. Introducing a legume like red or white clover into the mix can easily raise that percentage by 3 to 4 percentage units.
Additionally, Hall noted, pastures containing at least 35 percent or more legumes in the stand will not require annual nitrogen fertilizer application. Research has shown red and white clover varieties can contribute anywhere from 50 to 200 pounds of nitrogen per acre yearly.
“The legumes produce enough nitrogen to support the grasses,” Hall said.
For a typical grass pasture yielding approximately 3 tons per acre, Hall said, a single annual nitrogen application of 150 pounds per acre would be common. At today’s fertilizer prices ($290 to $412 per ton), the addition of legumes into their pastures could potentially save farmers $22 to $31 per acre annually.
“Multiply that savings by the number of pasture acres you’re managing and you can see pretty quickly that planting some clover provides some nice returns, especially given the inexpensive seed cost,” Hall said.
Typically, Hall noted, red or white clover are the legumes of choice when it comes to frost-seeding. They’re common, easy to attain, and have proven success establishing with this planting method. Clover species such as arrowleaf, berseem, balansa, and subterranean clover can also be used. Legumes like alfalfa and birdsfoot trefoil do not usually result in the same degree of success.
Whatever specific clover species pasture managers choose, Hall explained, it should be a type that meets the goals for their pastures. In general, red clover with its larger leaves and taller height works best for hayfields. In pasture situations, a more prostrate-growing species like white clover is ideal. Consult your local extension agent or seed sales representative to determine which varieties are best suited to your region.
Like any new seeding, end results can be variable. To improve establishment success, Hall offered a few key strategies to better the likelihood of getting a good clover stand.
While there is not much that needs to be done ahead of time, Hall said, producers may want to graze pastures tightly the fall before they plan to frost-seed clover. In addition, he pointed out, it’s best to wait until pastures have gone fully dormant before grazing. This will open up the plant canopy and allow seeds to have better seed-to-soil contact when it comes time to plant, while also not weakening the stand.
Hall recommended graziers calibrate their broadcast seeder ahead of time so pastures will not be under- or overseeded. Overseeding, in particular, adds to the cost. Typical frost-seeding rates for both red and white clover range from 2 to 6 pounds per acre.
Along with equipment calibration, determine the throw width of the seeder. Small-seeded forages such as clovers do not spread as wide as people expect. This can result in uneven seeding.
Freeze-thaw cycle needed
Lastly, the forage specialist noted that the biggest factor to get a successful clover stand lies in having the right weather and timing.
“You need that freezing and thawing cycle where it freezes at night and then thaws during the day,” Hall said. “This freeze-thaw cycle causes little ice crystals to form in a sort of honeycomb in the soil and gives seeds a place to fall into and enhance seed-soil contact.”
In Hall’s state of Pennsylvania, this period usually falls sometime in February. Depending on how far north or south producers live, he says, this ideal window could occur earlier or later in the year.
“We usually have a period where it warms up and the snow melts, then, later on, we get the freezing and thawing happening,” Hall said. “That’s perfect if you can hit a period like that. Keep in mind though that some years you just won’t get that, it just thaws and the window is not there.”
Another timing-related tip is to make sure seed is broadcast while the ground is still frozen.
“If you wait until 10 a.m., you’re too late and the soil will start to get slimy and slippery,” Hall said. “Get out there at daylight, do the frost-seeding, and then come in and have breakfast.”
In Hall’s experience, it is the farmers who are also successful graziers who will reap the full benefits of frost-seeding clovers. Through proper management, clovers can boost pasture forage production and quality for several years. When pastures reach a point the clover starts to thin out, just frost-seed again.
This article appeared in the January 2018 issue of Hay & Forage Grower on page 12.
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