Scrape the dry mud off the white garment with a plastic spoon or butter knife. Try to remove as much mud as possible without damaging the fabric.
Fill a bucket half full of water. Add one-half cup of dishwasher detergent. These products are made for dishwashers.
Put the muddy white garment in the bucket. Let the garment soak overnight
Make a cleaning solution of 4 cups warm water, 1 cup borax and 1 cup baking soda in a bucket. Place the muddy item in the bucket and let it soak for two hours. This is a faster method of cleaning whites caked with mud.
Rinse out the garment in clean water after soaking for the prescribed amount of time. Make certain all the mud is gone.
Put the white garment in the washing machine with other white or light clothes. Wash as usual with regular laundry detergent.
Check to make certain entire mud stain is gone before placing your garment in the dryer. If the stain is not gone, the heat only sets the stain in more.