Bone meal is the most readily available way to get phosphorus in your garden. It can be found in fertilizers or used with other products to mix up your own, so that you can control the levels of each nutrient that goes into your yard. If you want to make your own phosphorus fertilizer, the easiest way is to make your own bone meal. You can use scraps saved from your kitchen table so that you have one less thing going to waste.
Dig a trench 2 feet deep and lay wood inside. Lay wood only a foot high so that you still have a foot of trench above it.
Create ledges in the sides of the trench by digging into the sides. You can use a trowel to do this. Cut them into the sides about 1/2 a foot down.
Slide a metal grate, like what would be used on a grill, into the trench. Let it rest on the ledges you dug in the sides. This is the set up to burn the bones.
Lift the grate up to start the fire, then replace the grate.
Place the bones on the grate and let them cook. The high temperatures of the fire will burn off unwanted debris.
Test a bone every once in a while for softness. If the bone can be crushed easily with a mallet, then the bones are done. Put out the fire.
Pound the bones with a mallet to crush them up as much as you can. Mix the bone meal into the soil to add phosphorus.