By Victor Shelton
Adding legumes to pastures adds a lot of benefits. They are a nitrogen source for the grass, help boost the pasture’s overall forage quality, add diversity to the stand that in the long run helps improve soil biology, and provide some important pollinator habitat.
Frost-seeding a stand of legumes is certainly one of the least expensive ways to enhance your pastures. It’s basically the process of broadcasting legume seed onto the soil surface during the winter dormant months. The ideal time is usually somewhere between Christmas and Valentine’s Day.
If I had my choice, I would wait until there’s a light snow on the ground and then sow the legume seed. The snow serves two good purposes. One, it helps “catch” the seed and transport it to the ground; and two, it serves as a great marker for the path of the tractor or ATV as it moves through the pasture.
Frost-seeding relies on the freezing-thawing action of the soil, which causes honeycombing of the soil surface with ice crystals. This causes the soil surface to expand and contract, allowing small seed to find a route into the ground.
If you know you’re going to frost-seed legumes into a pasture, I would recommend the following approach: After the forage has become dormant, graze it down to 3 or 4 inches to remove any excess growth. That will allow the seed to find its way to the soil surface more easily and wait for that freezing action. Grazing closer to the soil surface also helps depress early-spring growth of the grass, which will give legume seedlings a fighting chance.
Don’t hit those newly seeded fields with nitrogen in the spring either. All this does is promote the established grass to grow, and reduce those new legume seedlings’ chances. They won’t have the root base or energy stored up to compete with established grass — especially if that grass has received a boost of nitrogen!
Keys to success
Slightly higher seeding rates for frost-seeding than for conventional seeding is a general rule. White clover can be seeded at 1 to 1.5 pounds per acre. White clover is a lot smaller seed than red clover and will be around longer. You can get it on too thick, and yes, I know, it’s hard to seed that small amount!
I’ve found that mixing it with another seed as a carrier works well. You can also mix the seed in with fertilizer or some pelletized lime. Don’t use fertilizer with nitrogen, and watch the amount of DAP you might apply.
Red clover should be seeded at 6 to 8 pounds per acre, birdsfoot trefoil at 5 pounds per acre, and common lespedeza with hulled seed at 10 pounds.
All legumes should be inoculated with the appropriate inoculants for that species to ensure proper bacteria, good germination and growth.
Frost-seeding legumes into your pastures provides a lot of benefits that can pay dividends.
Editor’s note: Frost-seeding legumes is a time-honored practice that dates back to dairymen “walking-on” red clover into wheat with a horn-type or hand-crank seeder. Follow Shelton’s guidelines to help it work for you today.
Shelton is a state agronomist and grazing specialist with the Natural Resources Conservation Service. He is also a contributor to Indiana Prairie Farmer’s Salute Soil Health column.