// Definition
The practice of layering multiple calcium sources with different solubilities in a soil mix to provide sustained calcium availability across the entire growing cycle, from fast-release gypsum to slow-release volcanic rock dust.
// From the Episode
Russ explained the system: gypsum (calcium sulfate, highest solubility, also brings sulfur for terpene/thiol production), wollastonite (calcium silica, medium-slow release, microbial dependent), bone meal (calcium phosphate), and basalt/volcanic rock dust (remineralizes over months to years). Calcium is the highest-ppm nutrient in leaf tissue despite being classified as 'secondary.'