Eli Weaver frost-seeding his pasture.
Forage & Grains
Renovating Pastures with
By Dave Wilson, Forage Research Agronomist at Kings AgriSeeds
Added April 3, 2013. Frost seeding has traditionally been an economical way to use legumes to thicken an existing grass stand or to establish a clover mix in an overwintering small grain stand (wheat is the most common, but rye and triticale are also frequently used). In some cases, thinning alfalfa stands can also be improved with a frost-seeding of clovers.
For pasture application, if the conditions are right and it is managed properly, it can be an opportunity to renovate a sparse pasture without tillage. Driving over the ground when it’s frozen, one can avoid the rutting and compaction that comes later as the soil softens. A well-frozen soil also allows the seed to bounce when it hits the ground, for broad, even dispersal.
Midwinter is the perfect time to consider frost seeding to improve perennial pastures, especially when a cold spell (without ice and snow) hits that leaves the ground hard enough to drive over easily. In southern states, February through early March is considered the ideal time frame. In Pennsylvania and New York State, late February through early March is acceptable, and further north, the window can extend into early April.
Perhaps the most important consideration is that your soil is exposed and the sward has space to support additional seedlings without too much competition. This means that the existing stand should be somewhat sparse or closely grazed.
Frost seeding, like any seeding event, requires adequate seed-to-soil contact, and this is usually achieved through the “honeycombing” effect of common wintertime freeze-thaw cycles. The best time is when soil is frozen in the morning and thaws during the day. The ground’s expansion and contraction with frost heaving efficiently works the seed into the soil, especially small round seeds such as clover, as it repeatedly creates cracks, splits, and holes in the soil surface. Larger seeds like alfalfa, crimson clover, and most grasses have much less success in establishing, since the larger seed is less effective at making its way to the needed soil depth. Some smaller-seeded and hulless grasses can work, however. Those with the highest probability of success include timothy, Kentucky bluegrass, and hulled orchardgrass.
Clover seed on frozen ground.
Alfalfa can work in some situations with some soil types that freeze and thaw more dramatically. Results are not consistent over varied soil conditions and locations, however, and a poor stand is likely. Soils expand and contract differently depending on their content of sand, silt and clay. Soils with a higher sand content do not hold as much moisture close to the surface, and a drier soil will not expand and contract as much. Clover seed has much more predictable success across all soil types.
In a pasture or hayfield situation, a chain drag or light disking can help open up the soil if needed. The seed can be spun on with a broadcast seeder. This is often done with a three-point hitch-mounted seeder. A good amount of the pasture’s soil should be exposed by a late fall close grazing or mowing, which provides ample opportunity for seed-to-soil contact of the broadcast seed. A bunch-type grass like orchardgrass typically leaves more exposed soil than a sod-forming grass, making it more receptive to frost seeding.
For frost seeding into an overwintering small grain such as barley, wheat, triticale or rye, there is usually bare ground between the drilled rows of the small grain during the winter, when the freezing and thawing occur and the clover can get worked into the soil. The clover germinates in spring and begins to grow under the canopy of the small grain. The canopy is opened after the small grain is harvested in summer, and the small legume seedlings are released from the competition with the small grain. The first cutting of the clover hay is often termed “stubble hay” because it will have some small grain stubble in it. The clover hay will over-winter and give a spring hay cutting or a nitrogen-rich green manure before corn the following year.
It is important to assess the canopy and soil coverage before beginning, however. Depending on region and conditions, an earlier-planted small grain like winter barley can tiller abundantly and give almost complete soil coverage by late winter, making frost-seeding impossible. Later-planted small grains that have plenty of exposed soil between the rows are ideal. The field should have at least half of its soil exposed.
Red clover is often considered an optimal choice for frost-seeding, since it has superior seedling vigor and is tolerant of varying conditions. Other small-seeded legumes such as white clover, yellow blossom sweet clover, white sweet clover and alsike clover also will work.
Hand-spinning has been a trusted frost-seeding technique for generations and keeps coming back into fashion; even farmers with extremely large acreage used to walk their fields at dawn broadcasting seed until the ground softened up, usually by late morning.
Dave Wilson is a Forage Research Agronomist at Kings AgriSeed. You can reach Dave by Email or Phone at: email@example.com or call him on his cell phone at (717) 682-1679. To learn more about Kings AgriSeed, go to www.kingsagriseeds.com