We usually suggest applying the fertilizer, then putting the horse out after it rains, if possible. It is usually fine to put a horse out right after fertilizing, but this is a safeguard. You should also be sure to read the label directions. All fertilizers are usually safe since they most likely contain nitrogen, phosphorus, and potassium, which will be absorbed by the grass. You should do a soil test (contact your local Cooperative Extension office) to be sure that you are applying what is needed in the proper amounts before spending money on fertilizer that you may not need.
