Never graze horses on grasses that have been treated with fertilizers or weed control products labeled for lawn use. In fact, it may be illegal to use these products on pastures or lawns that are used for grazing. Contact your equine veterinarian or county agricultural extension to learn what fertilizers, weed control products and pesticides are best for your pasture.
o Lawn fertilizers are frequently time-released products, slowly disbursing nitrogen into the lawn for weeks. The pelletized fertilizer can exist on the soil surface for several weeks. Nitrogen is, in large quantities, toxic to your horse. Even in lower quantities, it is very irritating to your horse’s stomach and a common cause of spring colic.
Pasture fertilizers also contain nitrogen but they are formulated for quick absorption into the soil. Even so, keep horses away from newly fertilized fields for at least three weeks. Be sure the grass has greened up and grown to a minimum of 3″. Pasture fertilizer is best applied when rainfall is imminent.
o Lawn weed control products are not subjected to the rigorous testing that is required for pasture products.
o Also be aware that many lawn pesticides were registered before 1972 and never tested for many health hazards such as carcinogenicity, neurotoxicity, and environmental dangers. Lawn chemical companies are not required to list all the ingredients on their containers and many toxins are listed on the label as “inert”. These “inert” ingredients can include benzene, xylene, components of defoliants like Agent Orange, nerve gas type insecticides and artificial hormones.
If you truly need to graze your lawn, manage it as a pasture and only use agricultural fertilizers, herbicides and pesticides that are labeled for pasture use.