After cutting down a fir tree, you are left with a tree stump. Because the root system is still alive, so is stump. The root system could still cause suckers or new trunks to grow out of the ground. One way to kill the tree stump and the root system is to rot it. You can use water to kill the stump over the course of a few weeks. This makes removal of the stump and the root system easier to complete.
Cut the stump as close to the ground as possible with a chainsaw.
Drill several 1/2-inch holes into the top of the stump with a hand drill. Go as deep as you can but no less than 2 inches deep. On an average-sized fir stump, drill seven or eight holes.
Fill the holes with water, and then pack the holes with a fertiliser high in nitrogen. Use fertiliser with the highest level of nitrogen you can locate. Soak the immediate area around the stump with a garden hose.
Place a tarp over the stump and weight it down with a few heavy objects. The tarp holds moisture in to keep the stump from drying out. This improves the speed of the rotting process.
Cover the plastic with organic mulch, and then wet the mulch using the hose. This creates heat and helps the stump retains moisture, both of which help speed up the rotting process.
Remove the mulch and plastic once per week, refresh the water and fertilisers in the holes, and replace the plastic and mulch. This ensures the stump stays wet throughout the process. Continue this until the tree stump shows signs of decay, or you can easily pick the stump apart with your hand.
The length of time it takes to kill the stump depends on the diameter of the stump and its relative health when you started rotting it. The moisture and nitrogen content in the fertiliser also have an effect on the rotting speed. It can take several weeks to several months to completely rot a stump.