pH below 7. In alkaline soil, adding bone meal may therefore provide considerably less benefit.
This is another reason a soil test can be useful before repeatedly adding phosphorus.
What About Charcoal?
The original recipe also recommends crushed vegetable charcoal.
Charcoal-based soil amendments can have horticultural applications, but ordinary charcoal shouldn’t automatically be treated as a complete fertilizer. Products also vary greatly depending on how they were manufactured.
Most importantly, don’t simply crush up charcoal briquettes containing additives and assume they’re suitable for
