How Rock Dust and Biochar Work Together to Remineralize Soils

Rock Dust & Biochar

We’ve written previously about the positive benefits of using volcanic basalt to speed the composting process. (See “Charge up your compost pile with nutrient-rich volcanic rock dust” and “Add rock dust to compost to feed your plants a balanced diet.”)

Rock dust serves as food for the millions of beneficial microorganisms that feed on each other and help break down organic matter. More microbial activity means more heat, and more heat leads to faster and more efficient composting.

Rock dust isn’t just a great complement to compost, however. It is also highly effective in helping improve soil’s health and fertility when combined with biochar, a solid material rich in carbon that was used as a traditional soil amendment for thousands of years. Indeed, evidence of “terra preta,” or “black earth,” dating back to the Pre-Columbian era, is still visible in the Brazilian Amazon.

Like rock dust, biochar has seen a recent resurgence as more people become aware of sustainability methods from the past—and understand their role in our future. When used together, they help the remineralization process by ensuring that plants have a steady supply of essential minerals and nutrients.

It works like this: Rock dust weather slowly, releasing essential minerals and trace elements into the soil over time where they are readily accessible to plant roots when they need them. Biochar helps keep these important minerals from leaching away too quickly by acting like a sponge whose absorbent surfaces also provide a safe place where beneficial microbes multiply and thrive.

One of the most effective ways to use rock dust and biochar is to mix them into your compost. For more information and links to recent research involving rock dust and biochar, read “Biochar and Rock Dust for Nutrient Dense Food, Soil Fertility Restoration, and Carbon Sequestration” at


When looking for a soil amendment made of volcanic basalt, look for a high-quality product that is listed by the Organic Materials Review Institute (OMRI) for use in organic production. One product that meets this standard is Cascade Minerals Remineralizing Soil Booster which is made entirely in the USA from all-natural volcanic basalt from Central Oregon.