Crushed basalt can be used as a substitute for mined fertilizer that would need to be applied anyway, notably potassium and phosphorus. It is one of the reasons

Crushed basalt can be used as a substitute for mined fertilizer that would need to be applied anyway, notably potassium and phosphorus. It is one of the reasons volcanic soils tend to be fertile. The rock leaches significant quantities of mineral that are important for plant growth.