Bone meal

Bone meal is a powder of ground animal bones and slaughter-house waste products, used as a dietary supplement to supply mainly phosphorus and calcium, being roughly 10–15% phosphorus, 0-10-0 to 3-15-0 NPK and 20-25% calcium.

Before Liebig, the expansion of agriculture had depleted the soil of essential nutrients. In desperation, farmers collected the bones from major battlefields like the Battle of Waterloo and the Battle of Austerlitz to crush them and refertilize the soil.

— Wikipedia.

This fertilizer can be made by processing animal bones such as chicken or fish—easier as smaller—and/or beef and pork, into a fine powder or granule. The basic recipe is as follows:

1. clean the bones, removing as much fat and meat as possible, as well as cartilage.
2. soak them in water for a few hours to loosen them
3. boil raw bones in a pot of boiling water for 1–2 hours to sterilize, soften, and remove remaining tissue. Alternatively, roast bones in an oven at 200°C for 30–45 minutes to sterilize and make them brittle. This is important to kill pathogens and make bones easier to grind.
4. dry the bones, 95°C for 2–4 hours, until bones are dry and brittle. This makes them easier to grind and less likely to spoil.
5. grind the bones, first smashing bigger pieces with a hammer, then grind into a thin powder. Sieve and regrind or dispose from larger chunks.

Then this can be used as a fertilizer: 1–2 tablespoons for a young tree. Sprinkle evenly around the drip line (the area under the outer edge of the canopy), admixing with the soil or covering with compost. Water thoroughly to help nutrients penetrate the soil. Use sparingly (once or twice a year).

Bone meal works best in slightly acidic to neutral soils (pH 6.0–7.0).