Time for Frostseeding Clovers is Here

Posted: February 3, 2016

Frostseeding is a technique that can be used to establish red and yellow clovers. The management and benefits of using clovers in the rotation are described.

February is upon us, the days are growing longer, and it is time to get ready for frostseeding of clovers into small grains. Planting clovers into a standing small grain crop is a method of relay cropping, where you make very good use of the growing season by starting a new crop before the previous one is harvested.

Clovers are great soil improving crops, having taproots and fixing atmospheric nitrogen. This nitrogen can benefit the next crop. The clovers can also be harvested as forage. The practice is quite successful because seed-to-soil contact is obtained through natural freeze-thaw cycles that create a ‘honey combing’ of the soil surface in the frosted early mornings after which the soil thaws which covers up the small clover seeds with a tiny layer of soil. The clovers that are suited for this practice include red clover and sweet clover. Both are cold tolerant so they will not be killed by frost.

Red clover is a short-lived perennial, while sweet clover is a biennial. Red clover is a well-known forage, while sweet clover is known as a soil improver, because of its taproot that can help create large pore spaces in the soil. While red clover is known as an excellent forage, caution needs to be paid when using sweet clover as forage because of its coumarin content. Coumarin is a blood-thinning, anti-fungicidal, and anti-tumor compound found in sweet clover, strawberries, lavender and cherries, among others. Therefore, it is important to avoid a pure diet of sweet clover for your animals. When mixed with other forages it is not a problem to use sweet clover as forage. Use about 10-15 lbs./A of clover seed when broadcasting it.

Make sure the seed has been inoculated with clover rhizobium (for red clover) or alfalfa rhizobium (for sweet clover) if clover or alfalfa has not been grown in the field for a while. Make sure you spread the seeds evenly using a cyclone spreader, spinner spreader or drop box. It is not recommended to spread on snow because the seeds can be carried away when the snow melt runs off.

It is important to avoid soil compaction. Since the soil is very moist right now it is advisable to spread the seed early in the morning when the top of the soil is frozen. When you notice that the soil is thawing, get out of the field immediately so you don’t damage the soil. Do not use herbicides to control weeds in your small grain after frostseeding clover.

Although rarely a problem, you may have to lift the combine head a tad to avoid getting a lot of clover into your small grain straw at harvest. After small grain harvest you should have a nice stand of clover coming up. Monitor the clover stand in June. If you see a lot of weeds coming up it is advisable to mow the clover stand in July to avoid weeds from setting seed. Mowing is advisable anyway to make the clover branch out more. If all goes well, you may harvest clover in the fall for haylage. Or you can just let it go and terminate it next year prior to a nitrogen demanding summer crop like corn, sorghum, or sudangrass. The nitrogen fertilizer value of the clover is typically 80 lbs. N/A for next year’s crop. Our research has also shown a typical yield boost of 20 bu/A in corn grain above and beyond the nitrogen value due to the soil improvement obtained by the clover.

Contact Information

Sjoerd Willem Duiker
  • Associate Professor of Soil Management and Applied Soil Physics
Phone: 814-863-7637