JEFF BURBRINK
Extension Educator, Purdue Extension Elkhart County

Jeff Burbrink

GOSHEN — A time-tested technique to improve pastures is frost seeding. Typically, frost seeding is done in February in our area in pastures that are less than 30 percent legumes. Frost seeding is also common in small grain fields such as wheat or oats, to produce some additional forage for the animals later in the summer.

The typical plants used for frost seeding are red clover and sweet clover. Clovers are great for the soil. They have lengthy taproots and the ability to fix atmospheric nitrogen in the soil. If it has been a while since red clover or sweet clover have been raised in the field, it is advised to inoculate the red clover with clover rhizobacteria, and the sweet clover with alfalfa rhizobacteria to insure the nitrogen fixation can take place.

Frost seeding uses the natural freeze/thaw cycle of the soil to place the seed in a good location for establishment.  The seed is spread on the surface, and as the soil freezes and thaws, it is gently covered by soil. Both red clover and sweet clover are cold tolerant, so the cold will not kill the germinating plants.

There have been times this past few weeks where the soil surface has been thawed because air temperatures have been well above freezing in the afternoon. When seeding under those conditions, it is best to seed earlier in the morning to avoid soil compaction.

Most people seed with a cyclone type spreader at a rate of 10-15 pounds of seed per acre. Red clover is known as an excellent feed, but care should be taken to not allow the sweet clover to take over the area. Sweet clover contains a chemical called coumarin, which is a blood thinner, but this is rarely a problem when used as a mix in pastures.

In some years, the clover can grow quite well, and at wheat or oats harvest, you may have to lift the head a bit to avoid pulling the clover into the grainhead. If you start to see a lot of weeds in the small grain stand, avoid spraying herbicides or you will damage the new seedling clover. Instead, mow the clover stand in July, to keep the weeds from going to seed. This also has the effect of causing the clover to branch out more.

Don’t expect either red clover or sweet clover to stick around long. Red clover is considered a short-lived perennial plant in our region. Heavy grazing or hay making generally reduce red clover stands significantly in two years.

Sweet Clover is a biennial plant, meaning its life cycle is 2 years long. It is known as a slower grower that first year, developing a deep, soil building root system. The second year of its life, the plant can grow very tall.

Sweet clover has a high growing point, so if you want regrowth after cutting or grazing, leave plenty of stem buds on 6 to 12 inches of stubble. You increase the risk of killing the sweet clover plant by mowing or grazing heavier stands at shorter heights.