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Now is the time to frost-seed clover.

Broadcasting clovers into a standing small grain crop is a method of relay cropping, where you make great use of the growing season by starting a new crop before the previous one is harvested.

Extension agronomist Sjoerd W. Duiker explains while broadcasting is not the most foolproof method of establishment, this is one of the scenarios that more frequently results in success.

The season is cool and the soil moist, so the seedlings are less likely to dry out, while freeze-thaw action helps improve seed-to-soil contact.

Clovers have small, round and relatively heavy seeds that drop through the small grain canopy to reach the soil.

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 clovers that are especially 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 massive 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 species, it is not a problem to use sweet clover as forage.

Use 10-15 pounds per acre 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.

If the soil is very moist, it is advisable to spread the seed early in the morning when the top of the soil is frozen, to avoid soil compaction.

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 frost-seeding 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 in the field. 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 prevent 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 pounds per acre for next year’s crop. Our research has also shown a typical yield boost of 20 bushels per acre in corn grain above and beyond the nitrogen value due to the soil improvement obtained by the clover.

Leon Ressler is a Penn State Extension educator based in Lancaster County, Pennsylvania.

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