Mud and soil are greyish, brownish, reddish or yellowish. They are absorbed and built-up types of stains that can contain soil with greases and oils, as well as clay and iron.
Brush or scrape off as much as possible.
Apply detergent solution, blot.
Apply ammonia solution, blot.
Apply vinegar solution, blot.
Apply pressure to the spot with a spatula or the back of a tablespoon to work spotting solution deep into spot. DO NOT SCRUB as this may cause nap distortion of the fiber.
Rinse thoroughly with water, blot until dry.
If stain remains, apply a "paint oil and grease" remover and dry cleaning solvent alternately, blot until dry.
(Dry cleaning solvent contains volatile organic compound. Use carefully in strict accordance with manufacturers' instructions. Use in well ventilated space and avoid products containing perchlorethylene.)