Rock dust adds minerals to the soil, which soil often misses due to common intensive agriculture. The soil degrades, yields less and is exhausted: the biology is out of balance. This article discusses the contribution of rock dust to soil fertility.
Gino Smeulders is a soil geologist and specializes in soil fertility. As an expert, he knows how rock dust (small stone particles called soil minerals) can contribute to healthy soil. He feels that the importance and function of soil minerals remains underexposed in the current assessment of soil fertility.
What's the problem: natural weathering processes cause soils to become depleted in much-needed (trace) elements over time. Long and intensive agriculture tends to acidify soils and accelerate this process. In addition, the balance between chemical elements in soils is often not optimal anymore, for example due to too much chemical fertilization which is often focused on NPK only. As a result, other elements, which the soil also needs to function properly, such as magnesium, calcium, and essential trace elements are on the sidelines as they can be washed out or blocked by the fertilizer. A soil needs a complete foundation to be able to function, otherwise it starts to crack. What can solve this problem?
A fertile soil is a delicate balance of soil minerals, organic matter, moisture, air and soil organisms. The soil minerals are generally disregarded in soil science, but they form a very large stock of nutrients, which slowly become accessible to soil organisms and crops. Soil minerals also play an important role in neutralizing soil pH, increasing humus in the soil, and creating micro-habitats to support a diverse soil biology. Thus, when soil mineralogy changes it affects various soil properties, and leads to often misunderstood problems such as deteriorating soil structure, higher disease pressure and chemical changes.
Rock dust replenishes the soil minerals that are missing. Rock dust should not be just an unweathered soil, since most soils only contain small amounts of minerals that are chemically active and biologically available. Instead, a good rock dust contains a high amount of the minerals that the soil lost over time. In general, basaltic rock dusts will do an excellent job in resupplying the soil with a natural variation of essential bulk and trace elements. It also stimulates soil life, stabilizes organic matter, strengthens the long-term supply of all nutrients (except nitrogen) and gradually increases the exchange capacity of the soil. A major advantage is that the supply of rock dust is virtually unlimited in nature, and CO2 is drawn from the air when the rock dust slowly weathers in the soil.
But what exactly is rock dust? It is finely ground rock of volcanic origin. Where sediment is weathered rock, which helps soil fertility after flooding, rock dust is unweathered rock. After applying rock dust to the soil, accelerated weathering occurs (by chemical and biological soil processes), releasing mineral nutrients for the crop. However, not every rock contains the right amount of minerals in a form that is available to soil life and plants. Volcanic rocks with low silica content contain the most minerals. Some rocks from mountain formation are also very suitable. In general, sandstone, claystone or limestone are not a good option as these do not contain the right kind of minerals.
Rock dust contributes to systemic changes in the way the soil is treated. Instead of only combating symptoms with chemical products, rock dust helps to restore soil nutrients and support soil biology on the basis of natural principles. This contributes to long-term soil fertility.