To get dirt stains out of clothing, use a plastic knife to remove any caked on dirt, a toothbrush to rub the stained area gently with a commercial stain treatment product (liquid dish soap will work as well), and then run the item through a regular wash cycle. Treat a dry dirt stain as soon as possible, otherwise it may become permanent.
Scrape off the dirt
Scrape off the loose dirt with a plastic knife. Brush the excess dirt off with a small toothbrush.
Rub in liquid dish soap
Apply liquid dish soap to both sides of the fabric, and rub it gently into the stain. Next add a small amount of water. Rub the stain on both sides with a toothbrush, working the liquid dish soap deep into the fabric. Let it soak for 1 hour. Repeat this process until the stain is no longer visible.
Wash the fabric
Place the fabric in the washing machine, laundering separately to prevent the stain from spreading. Use warm water and laundry detergent. Once the wash cycle is complete, inspect the fabric to make sure the stain is removed. If the stain remains, rewash the fabric. Don't place the fabric in the dryer if the stain is still apparent. Drying the stain sets it in and makes it harder to remove. Instead, allow the fabric to air dry.