Frost Seeding Works

The all terrain vehicle (ATV) roared up and down the field, ripping through the last snow drifts of winter. The passing vehicle slowed, the driver obviously wondering if his neighbouring farmer had finally lost his marbles.

But no marbles had been lost. Instead, the spinner on the back of the ATV threw grass seed across the frozen field, to be lost into the slowly thawing soil. This activity would pay off later on, resulting in vigorous new growth in a thickening sward of pasture.

Frost seeding is the name given to the process of spreading seed across fields in late winter and early spring. The thawing/freezing action in early spring acts to work the grass seed into the soil. Moisture from melting snow and spring rains helps the seed germinate. The new seedlings grow to thicken stands, providing more grazing for livestock.

Image of a field that has been frost seeded.
Frost seeding can introduce legumes to improve pasture quality

Recently (2009), at the Agriculture Canada Research Station at Kapuskasing, several fields were determined to have low or non existent legume content. The cows grazed existing grasses in the fall, leaving little residue. Red Clover seed was spread on the fields by ATV in April of 2010, while snow was still on the ground. The seeding rate was 10 lbs per acre. By early June it was evident that red clover now made up 50 % of the forage stand or greater in areas where previously there was no legume.

In 2011, red clover was spread in additional fields. This time the rate was cut to 5 lbs per acre, and the grass was not grazed off in the fall. Evaluation in the summer demonstrated that the red clover per cent increased only marginally (less than 15 %.)

Frost seeding is a concept that has been around for quite a while. The process imitates the natural process of seed heads shedding mature seed from plants onto the ground in the fall. While forage seed can be spread at any time, typical frost seeding now occurs in late winter/early spring. Farmers are afraid that seed spread in the late fall could germinate in a winter thaw, or be washed away in a spring melt. So usually the seed will be spread on the last melting snows of winter, or the frozen ground of an early spring day. The subsequent morning freezing and afternoon thawing works to lower the seed into the soil, ready to germinate in a sustainable environment as the soil temperature warms.

Frost seeding is especially beneficial in areas where the pasture or hay field has "run out" of legumes. Legumes provide extra yield, and quality in the field, as well as taking nitrogen from the air, and making it available in the soil for grass roots to use.

Clovers, trefoil and alfalfa are the legumes most used in frost seeding. The down side of alfalfa is a built in autotoxicity that allows existing alfalfa plants to kill any new germinating alfalfa seed. If there is existing alfalfa in a field, putting more alfalfa seed into the ground is counter productive.

Red clover and white clover stands can be effectively rejuvenated with frost seeding.
In the Kapuskasing trial, the application of 10 lbs per acre provided a dramatic increase in legume content. However, bear in mind that clovers can cause bloat. Managing pastures with thick clover stands can be a challenge.

An option would be to include 5 lbs of clover and 3 lbs of trefoil. Trefoil does not cause bloat, and provides the same nitrogen fixing capability as clover. However, It can be harder to establish than the clovers.

The experience at Kapuskasing, and research at Wisconsin demonstrates that having the cows graze off the pasture in late fall allows the seed better soil contact and more light to power the newly germinated plants.

Frost seeding can work to rejuvenate old stands. Frost seeding of legumes also adds their nitrogen fixing capabilities to the sod, thus reducing the need to purchase as much commercial nitrogen fertilizer. While frost seeding is not as effective a strategy to rejuvenate a pasture as ploughing and working up the land, it is a much cheaper alternative than plowing with conventional seeding. Its also a great the way to improve fields that are too rough or hilly to be worked by conventional tillage.


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