Late Winter Frost Seeding


Almost every year I am asked about frost seeding as a method of introducing forage legumes into hayfields and pastures. Maintaining legumes in hay fields and pastures is necessary for low cost forage production and to improve forage quality. Legumes are high in protein and digestibility improving forage quality, and they are able to capture atmospheric nitrogen through nitrogen-fixing bacteria. Legumes will indirectly supply nitrogen to the grass to maintain forage yields.


Maintaining legumes is more difficult than grasses. They are more prone to disease, insect attach, and winter injury. Maintaining soil fertility (P and K), high soil pH (above 6.0) and a proper harvest management schedule will assist legume survival. However, reseeding may still be necessary on occasions in part or all of the field. This can be achieved by conventional tillage, no-till or low cost frost seeding. Frost seedings are inexpensive, and when done at the correct time and managed properly are very successful yielding similar to conventional methods.


Frost seedings should be made in late winter when warm daytime temperatures alternate with freezing nights. Under these conditions when there is little snow, frost action will honey-comb the soil surface. The freeze-and-thaw action helps broadcast seeds get into the soil. Timing of such conditions vary in Massachusetts from year to year, however, frost seedings should be made from February to early March.


Frost-seeding works best if fields have been grazed or cut in the fall or winter. This opens the sod, allowing better soil-to-seed contact. If too much vegetation remains broadcasted seeds can become lodged or hung-up in tall forages and never reach the soil. Grazing or mowing the prior year's growth also reduces shading and competition between established plants and new seedlings. Late grazing will also diminish the vigor of weeds reducing their regrowth and competition in the spring. This will also minimize the need for herbicides often used in no-till establishment for weed control.


Red clover is ideal for frost seeding. It establishes rapidly, is winter-hardy and disease-resistant. Birdsfoot trefoil and ladino clover are slower to establish, but once established, are more persistent especially in rotationally grazed pastures. Alfalfa is not suited to frost seeding to thicken declining alfalfa hay fields since alfalfa is autotoxic, meaning alfalfa seed will not establish in old alfalfa stands.


If the plan is to over-seed every year, apply 2 lb. red clover seed/ac./yr. However, since red clover is a biannual, meaning it lives for two years, it can be  seeded every other year. In this case increase the seeding rate to 4 lb./ac. on pasture and 6 to 8 lb./ac. on hayfields. Add 0.5 to1 lb./ac. of ladino clover seed, especially when seeding pastures and even for hayfields. Birdsfoot trefoil at the rate of 4 to 8 lb./ac., can also be frost seeded and will be the choice when soil pH is less than 6.0 or on poorly-drained soils.


Frost seeding grasses should be avoided.  Lightweight grass seeds tend to get hung-up in existing vegetation more than legume seeds. Unless the seed makes soil contact it will not become established. In frost seedings we are relying on using frost  action to work  the soil,  prepare the seed bed, cover the seeds, and provide seed to soil contact. Where there is not sufficient frost action after applying the seed, allowing livestock to walk the pastures will aid trampling the seed into the soil surface. This should only be done with cattle when the soil is sufficiently firm so that the cattle do not pug the soil and push the seed too deep into the soil. Use of livestock to aid seed incorporation will be more important in late seedings or when seeds remain exposed.


Introducing legumes into pastures and hayfields will improve the quality of forage. Animals will need less high priced protein and energy supplements. Use of nitrogen fertilizer will be less thus the net return will increase. Re-seeding is crucial if stand productivity dropped in the fall. Knowing the cause of the decline however, is vital. If the decline was due to improper fertilization, disease or poor legume selection then these should be corrected.


Stephen J. Herbert

Dept. of Plant and Soil Sciences

University of Massachusetts Amherst

Crops, Dairy, Livestock News. Vol. 3:2, Winter 1998-99

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