The usual warning about Grazon 90 / Grazon Pro - it is highly persistent, in the sward and through animals’ digestive tracts. No problem if you only use your muck on pasture / meadows. But don’t use muck from animals that have grazed the treated sward or hay made from it (even months after treatment) on any broadleaved plants - gardens, veg plot, tomatoes, turnip patch, etc.