ATHENS, Ohio -- Frost seeding is viewed as a low-cost method for livestock producers looking to renovate pastures while increasing yields and improving quality with little commercial nitrogen.
Frost seeding involves broadcasting a grass or legume seed over a pasture and letting the natural freeze/thaw cycles of late winter and early spring move the seed into good contact with the soil. The best time to frost seed is usually from mid-February to the end of March.
"A basic requirement for frost seeding success is to make sure that the sod cover has been opened up, and that there is not much growth present to prevent the seed from coming into contact with bare soil," said Rory Lewandowski, an Ohio State University Extension educator for Athens County. "Generally, a pasture is prepared for frost seeding by grazing it down hard, although some light tillage or a close mowing could also be used."
Another frost seeding method involves combining frost seeding with hoof action, said Lewandowski.
"Under this seeding scenario, let your animals graze the paddock in early March to scuff up the soil and open up bare areas in the sod. At this point, broadcast the forage seed across the paddock. Keep the animals in the paddock another couple of days and let them continue to graze and trample or hoof in the seed," said Lewandowski. "This method seems to work best with sheep because they don't trample the seed into the soil too deep."
In general, legumes tend to work better for frost seeding compared to grasses, said Lewandowski.
"This might be because legume seeds are typically heavier than grass seeds and can reach the soil level more easily," he said. "Another advantage to frost seeding a legume is that legumes 'fix' nitrogen typically in excess of their own needs. The existing plants use the excess nitrogen, which improves their quality as a feedstuff. Once legumes become established in a stand of pasture and compose 25 percent to 30 percent of the stand, there is really no need to apply supplemental nitrogen."
The following are some of the more popular legumes used for frost seeding:
• Red clover -- Red clover is probably the most widely used forage species when it comes to frost seeding. Red clover has high seedling vigor, is tolerant of a range of soil pH and fertility conditions, and tolerates drought better than white clover. However, red clover is a short-lived perennial, typically persisting in a stand for only a couple of years. Research is under way to find varieties with higher longevity.
• White clover -- White clover is a perennial clover and begins its production in the cooler spring weather. White clover is a low-growing legume, meaning that in order for the white clover to thrive, the grass must be grazed down shorter so that light can get through.
• Alfalfa -- Alfalfa has been tried as a frost seeded legume with variable results. Alfalfa has higher fertility requirements than clovers and it also requires a soil pH above 6.5 for best establishment results.
• Birdsfoot trefoil -- Birdsfoot trefoil is a persistent perennial once established, but can be slow to establish, often not showing up in a stand until the second year after frost seeding.
• Annual lespedeza -- Annual lespedeza is receiving more attention as a frost-seeding legume. Annual lespedeza is a non-bloating legume that is drought tolerant. Although annual lespedeza will tolerate acidic soils (pH 5.0 to 5.5) and low phosphorous level soils, it will also respond to applications of lime, phosphorous and potassium. However, applications of nitrogen will decrease lespedeza yields. Lespedeza is a warm-season forage that can be used to fill in the "summer slump" period that cool season grasses experience.
Although grasses do not generally work as well as legumes, research has shown that perennial and annual ryegrasses and orchardgrass are suitable for frost seeding.
For more information on improving pastures with frost seeding, refer to the fact sheet on OSU Extension's Ohioline at http://ohioline.osu.edu/anr-fact/0014.html.