As of: March 13, 2024, 8:00 a.m
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Primary rock flour enriches the soil with natural minerals and improves soil quality.
But there are differences as to which stone powder makes sense in each case.
Primary rock powder, often also called rock powder or simply stone powder, is obtained by grinding stones that are often millions of years old.
Volcanic rock is usually used as the starting material because it contains a particularly high amount of minerals.
The powder is very fine, the grain size is well under 0.1 millimeters.
Rock powder contains almost no main nutrients and is therefore not considered a classic fertilizer.
Instead, it serves as a mineral soil additive that enriches the soil with valuable trace elements and thus improves soil quality.
What is rock powder made of?
The composition of stone powder varies greatly depending on the source rock.
Lava rock, for example, contains significantly more iron compounds than basalt or diabase powder.
The main components are:
Silica (silicon): Makes plants more resistant to pests.
Calcium: Ensures efficient water absorption and transport into the cells.
Magnesium: Needed to form chlorophyll and process carbohydrates, proteins and vitamins.
Iron: Is important for plant photosynthesis.
Trace elements: molybdenum, manganese and various metals
Stone dust is an excellent soil activator © Angle / Imago
This is how primary rock flour improves your soil
Although rock powder is not fertilizer, it enriches the soil in other ways.
This puts them in the category of soil improvers (promotional link).
The main benefits of having stone dust in your garden are:
Stone dust as a soil activator
Thanks to its fine grain size, stone dust can bind certain ions and release them to microorganisms.
This supports their metabolism and in turn helps to provide nutrients for the plant from the organic matter in the soil.
Stone powder can help fill tired soil with life again.
Supporting organic fertilizer
Primary rock flour improves the efficiency of organic fertilizers such as Terra Preta or compost tea.
The trace elements contained in the rock dust help in the formation of enzymes and thus support the plant's metabolism.
Buffering effect for the pH value
A stable pH value is extremely important for plants and strong fluctuations can lead to major problems.
Rock powder has a buffering effect here.
This means that they can compensate for fluctuations to a certain extent.
Formation of clay-humus complexes
Rock powder, together with organic material, forms clay-humus complexes.
This creates an ideal soil structure that, on the one hand, holds water very well, but on the other hand also allows sufficient ventilation.
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Which rock powder is helpful for which soil?
Which rock powder is suitable for your soil depends on the pH value of your soil.
Acidic rock powder is suitable for alkaline soils with a high pH value.
On acidic soils with a low pH value, alkaline stone powder makes sense.
Also, think beforehand about which plants you want to cultivate in the ground.
The minerals and trace elements contained in stone dust should suit the needs of your plants.
When dosing, always follow the manufacturer's instructions.
Lava flour
Lava flour contains many minerals and iron compounds.
This makes it ideal for regenerating heavily stressed soils.
It is also the best choice for heavy-feeding crops such as tomatoes and eggplant.
Granite or basalt powder
These stone powders acidify the soil and thus lower the pH value.
They are ideal for compost heaps as they promote microbial life there.
The decomposing microorganisms then multiply more quickly and work more effectively, so that coarse biomass is broken down more quickly.
Diabase flour
Diabase flour is rich in calcium and greatly increases the pH value of the soil.
It also supplies the plants with silica, magnesium and iron.
It forms very stable clay-humus complexes.
And last but not least, it even improves the taste and shelf life of grown fruits and vegetables.
Bentonite
Bentonite consists of various clay minerals and is therefore sometimes called clay powder.
When combined with enough organic material, it forms particularly stable clay-humus complexes.
It is also the best choice for well-drained sandy soils as it helps the soil retain nutrients and water.
Zeolite
Zeolite is a strongly alkaline rock powder made from particularly porous volcanic rock.
Due to its high pH value, it should be used primarily on acidic soils.
There it improves water storage and has a positive effect on humus-forming microorganisms.
It is quite expensive, but used correctly it helps save fertilizer and water.