Frost Seeding Clover: Getting it Right! 

Legumes play in sustainable grassland ecosystems.  This is especially true at current fertilizer prices. Nitrogen prices have continued to increase (Figure 1). Currently, one pound of nitrogen as urea is coming in at $0.95.  The following article provides some practical suggestions for establishing and maintaining legumes in your pastures. 

Figure 1. Nitrogen price trends over the last 12 months.   

Soil test and adjust fertility.  In order for clover and other improved legumes to persist and thrive in pastures, we must create an environment conducive to their growth.  This starts with soil fertility.  Prior to frost seeding clover, lime and fertilize pastures according to soil test recommendations. 

Suppress sod and decrease residue.  The existing sod must be suppressed and plant residue reduced prior to frost seeding.  The reduction in plat residue allows seed to reach the soil surface where it can be incorporated by freezing and thawing events.  Sod suppression and residue reduction is best accomplished by hard grazing in late fall and early winter.  

Ensure good soil-seed contact.  Good soil-seed contact is required for seed germination and emergence.  In frost seedings, this occurs when freezing and thawing cycles form cracks in the soil surface, often referred to as a honeycomb.   

Seed on Proper Date.  Frost seeding is best accomplished in late winter or very early spring (February and early March).  Frost seeding is accomplished by simply broadcasting the seed on the soil surface and allowing the freezing and thawing cycles to incorporate the seed into the soil.  Success with frost seeding can be enhanced by dragging your pasture as or immediately after or as you broadcast the seed. 

Use High-Quality Seed and Adapted Varieties.  Use either certified or proprietary seed to ensure high germination, seed genetics, and low noxious weed content.  Do NOT use VNS or Variety Not Stated seed since there is no way to tell how it will perform in Kentucky. 

Choose clover varieties that have been tested in Kentucky.  The University of Kentucky has one of the most extensive variety testing programs in the country.  The 2021 variety testing results can be found on the UK Forage Extension website or by visiting your local extension office. 

Use correct seeding rate.  In Kentucky, a good mixture for frost seeding is 6-8 lb/A of red clover, 1-2 lb/A of ladino or grazing white clover.  On rented farms or where soil fertility is marginal, adding 10-15 lb/A of annual lespedeza to this mixture can be beneficial. 

Calibrate seeding equipment.   Maintain and calibrate seeding equipment prior to seeding.  Several approaches to calibrating small spinner seeders or no-till drills can be viewed on the KYForages YouTube Channel.  

Inoculate Legume Seed.  Most improved clover seed comes with a clay-based coating that contains inoculant.  Make sure that the seed is fresh and has not been stored under adverse conditions.  If the seed is not pre-inoculated, inoculate it with the proper strain of nitrogen fixing bacteria prior to seeding.  This is relatively inexpensive insurance that legume roots will be well nodulated and efficient nitrogen fixation will take place.

Control Seeding Depth.  Small-seeded forages should be placed than 1/4 to ½ inch deep.  If using a drill always check seeding depth since it will vary with seedbed condition and soil moisture status.  Placing small-seeded forages too deep will universally result in stand failures.  Since frost seeding broadcasts the seed on top of the soil, this problem is minimized. 

Check seed distribution pattern.  When using a spinner type spreader/seeder make sure and check you spreading pattern.  In many cases small-seeded forages are not thrown as far as you think.  This can result in clover strips in your pastures rather than a uniform stand. 

Use GPS guidance to eliminate overlaps and misses.  A recent study conducted at UK Research and Education Center in Princeton found that frost seeding without GPS Guidance resulted in a 35% overlap.  Using GPS guidance reduced the overlap to 3%. At an overlap of 20% and an overseeding cost of $30/A, a portable GPS unit will pay for itself in less than 250 acres.     

Control Post-Seeding Competition.  Not controlling post-seeding competition is one of the most common causes of stand failures.  One of the best management practices is to leave cattle on pastures that have been overseeded with clover until the clover seedlings get tall enough to get grazed off.  Then remove animals from the pasture and allow that clover to reach a height of 6-8 inches.  At that time the paddock can be placed back into the rotation.  If the existing vegetation is not controlled, the new clover seedlings will be shaded out. ~ Chris Teutch, Cow Country News