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How much clover seed is enough?

By Richard Barrett, Manager, Jimmy Carter Plant Materials Center, Americus, GA

Crimson clover plots growing at GAPMC

Planting the correct seeding rate for optimum production is a fundamental question farmers and landowners face for every crop. With crimson clover you find coated and uncoated seed available for purchase, but seeding recommendations usually specify a single rate for both types of seed.

Crimson clover is a popular cool-season legume grown in much of the southeastern United States. It is planted and managed for a wide-variety of reasons including: cool-season cover crop, grazing and forage production, and wildlife plantings. Seed is readily available across the entire area and several improved varieties exist that provide choices that help meet the planting objectives.

Seed coating has become a popular option for crimson clover seed. Seed is coated with an external material to improve handling, protect the seed, and to enhance germination and plant establishment. With crimson clover a specific clover inoculant containing a blend of beneficial nodulating bacteria is applied with the coating. Having the correct inoculant in contact with the developing seedling is necessary for the legume plant to produce nodules and fix nitrogen. The convenience and time savings of inoculated seed coating is attractive when purchasing clover seed.

When farmers choose coated seed, they need to consider the impact that the coating can have on seeding rate calculations. In many coated clover seed lots, the seed purity reported on the seed tag is below 50%, with at least half of the weight made up of the coating itself. The seed purity of many uncoated clover seed lots is above 80%. This difference in the purity of coated and uncoated seed may greatly influence seeding rate calculations and planter calibration.

Coated clover seed size on Left is compared to uncoated clover seed size on the right.  The penny in the center is for relative size comparison.

One way, farmers can account for the variation between seed lots is to use seeding rates and calibrate their planting equipment on a Pure Live Seed (PLS) basis rather than bulk seed. When basing seeding rates on PLS the seeding rates are adjusted to account for variations in germination and purity for each lot of seed. The calculation of seeding rates using PLS can result in a doubling of the seeding rate for coated clover seed due to lower seed purity caused by the addition of the external coating material. Since coating seed may result in improved germination and better plant health, PLS calculations may overestimate seeding rates for coated clover seed resulting in farmers planting more seed than needed and increasing their cost.

The Plant Materials Centers in Georgia and Mississippi are comparing the performance of seeding rates based on PLS to bulk seeding rates of coated seed and uncoated crimson clover seed. The variety ‘Dixie’ is being used because of its availability and acceptance across the southeast.  A standard base rate of 15 pounds per acre planted with a drill is being used. Pure Live Seed seeding rates of 100%, 75%, and 50% are being compared to the base rate of uncoated seed and coated seed. Canopy cover, plant height, and plant biomass produced is being measured to determine the effectiveness of the seeding rates. Our goal is to determine which seeding rates are most cost effective in producing acceptable biomass yields.

Close up view of crimson clover in bloom
 
Close up view of crimson clover in bloom

*DISCLAIMER - This feature article is specific to seeding rates for crimson clover. Crimson Clover should not be confused with Red Clover.  Both species have the potential to be a concern for horses.  Additional information on both crimson clover and red clover can be found in the Plant Guides below.

Cover Crops and Soil Health

The NRCS National Soil Health and Sustainability Team and Plant Materials Program are working together to improve our knowledge of using cover crop mixes to produce healthy soils.

Cover crops have the potential to provide multiple benefits in a cropping system. They prevent erosion, improve soil’s physical and biological properties, supply nutrients, suppress weeds, improve the availability of soil water, and break pest cycles along with various other benefits. The species of cover crop selected along with its management determine the benefits and returns.  Click here to learn more, download Plant Guides, technical documents, and cover crop selection tools.