1. Roast/toast crushed eggshells. I used a dry wok. Heat the finely crushed shells until they are black. Don't do this in the house unless you have a really good exhaust fan.
2. Soak roasted eggshells in equal volume of vinegar for two weeks until the vinegar dissolves the eggshells. The mixture will bubble and foam for a few minutes so don't immediately tighten the lid of the jar.
3. Dilute 1:20 parts water (2 tbsp/gal.) and spray on plants or water into the dirt around the plants.
4. This is best used during a specific period in the plants growth; such as just before flowering/fruiting. That said; calcium is important throughout the entire growing cycle.
This is a pretty easy process and takes about 30 minutes the first time. Don't forget; let the mixture sit for 2 full weeks.
What you describe creates calcium acetate not phosphate. Egg shells contain very little phosphorus so you're dissolving calcium in acetic acid.
ReplyDeleteThere is no need to ash them first, nor will it take more than a few minutes of stirring to dissolve them if they are crushed. Test with a pH strip if you like, the acid has reacted away almost immediately so more time sitting doesn't do much. If egg shells remain after the pH is above 6, add more vinegar a little at a time.
The best way to use this is the mix it into the soil before transplant so there is an equal concentration the plant doesn't absorb all at once but rather as the roots grow, unless the soil will be subject to enough rain to wash it out, then instead it can be applied to the soil surface at regular intervals with increasing dosage as the plant's needs increase.
I have to agree with anonymous on the time required. I was wondering why the eggshells had to be toasted too - I don't do that, and get good results. I just let the eggshells dry and crush them well, and use a mortar and pestle to make them very fine particles. It only takes a few minutes for them to dissolve. I always add more eggshells to ensure the acid is all used up. The remaining powder isn't wasted - add more vinegar and more eggshell powder, and repeat. An endless supply!
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