Cut as much off of the top of the stump as possible. Drill 1 inch holes 3 or 4 inches away from the edge of the stump. Make the holes about 12 inches deep. Drill holes in the top of the stump, angled at 45 degrees, to connect with the holes around the edge of the stump (see reference 2).
Fill the holes with the nitrogen fertilizer and let them seep into the water that is already in your stump. Fill the holes with more water if there isn't enough water in or around your stump (see reference 1).
Wait four to six weeks for the nitrogen fertilizer to take effect. Monitor the stump's progress over the waiting period until the stump is sufficiently spongy (see reference 2).
Use an axe to chop up the stump. Remove the cut wood and use a shovel to dig out any remaining roots or wood particles (see reference 2).