Richard Taylor, Extension Agronomy Specialist; email@example.com
Usually we think of white clover as a beneficial legume that can not only add protein to a grazing animal’s diet but can supply much needed nitrogen (N) to the soil that it shares with the companion grass in a pasture situation. However for the equine pasture manager, white clover often seems to take over the pasture and even out-competes pasture grasses. Where this is especially true is when horses overgraze the grass in a paddock, allowing white clover to establish since it is very adapted to close grazing conditions. The University of Maryland and the Horse Outreach Work Group (HOW) suggests limiting the amount of clover or legume to no more than 20 percent of a pasture. How can this be accomplished?
In general, legumes have tap root systems rather than fibrous root systems as is found in forage grasses. A fibrous rooted crop is much more efficient at obtaining soil N whether from organic matter mineralization or commercial fertilizer than is a tap rooted crop. White clover is also a relatively low growing crop since it spreads by stolons (rooted stems that hug the soil surface) and the only vertically growing parts are the flowers on peduncles and leaves on petioles. If not over-grazed and if soil N is available, grasses are able to grow above white clover and compete more effectively for sunlight. One of the ways we have to gradually reduce the density of white clover in a pasture is to manage the available N supply and try to reduce over-grazing.
To begin the conversion process, remove the animals when there is still 4 to 6 inches of regrowth in the pasture and immediately apply 30 to 50 lbs of N fertilizer. The fertilizer will be taken up more rapidly by the grass component of the pasture and because adequate leaf area remains, the grass will grow rapidly and shade the white clover plants. Allow the pasture to recover to 10 to 12 inches before grazing again and repeat the process if adequate soil moisture is available for growth.
Another option is using a herbicide to control the clover. A broadleaf herbicide like 2,4-D, which is sold under a wide variety of trade names such as Pasture Pro, can be useful in reducing the amount of white clover in a pasture and is labelled with no requirement that animals must be kept off the pasture for a specific period of time. There are environmental factors which must be observed, such as not applying it when the air temperatures is 80°F or above, when winds are gusty, and when the humidity is high. Although it might be more expensive, I suggest that it is best to hire a professional applicator to apply weed control products to protect yourself, your horses, and your neighbors since some herbicides are very volatile and can get into the air and move causing damage to neighboring sensitive plants.
After reducing white clover populations to the level you feel comfortable with, you should take precautions to manage the pasture so overgrazing does not occur in the future. By managing in favor of the grass component, the pasture manager should be able to control the amount of white clover in the pasture.