Primary rock powder

from Wikipedia, the free encyclopedia

Primary rock flour is a general name for a soil additive made from industrially ground rock. It is used for the general improvement of soil fertility and water retention capacity in home gardens, in organic fruit growing and agriculture as well as in viticulture.

The term is not protected by law. It can refer to the product of a grinding of a mineral group or to a mixture of different pre-produced rock powders. Composition, chemical and physical properties result from the goods declaration according to the fertilizer ordinance and the safety data sheet of the respective commercial product.

Parent rock

Depending on the original rock, a distinction is made between “acidic” and “alkaline” (basic) primary rock meals. These terms are essentially derived from a low (higher content of slate and granite) or a high calcium content in the primary rock powder. The pH values ​​vary, depending on the type of rock or mixture, between pH = 6.5 to pH = 13. For the cultivation of soils with a naturally high calcium content (clay, loam, loess), acidic primary rock flour and naturally acidic soils (sand, Gley , Podsol ) alkaline primary rock flour is used to achieve the most positive effect and activation of the soil life.

Frequently used parent rocks are diabase (alkaline) or basalt (acidic). The silicates and feldspars contained therein provide important minerals for plant growth in the long term due to slow weathering , especially iron , magnesium and potassium from the silicates and calcium and sodium from the feldspars, as well as others for cell structure, photosynthesis , the formation of vitamins, flowering and fruit important trace elements. These are manganese, copper, molybdenum, boron, nickel, zinc and cobalt. Primary rock flour enriches impoverished soils with trace nutrients, promotes the build-up of humus in the top soil layer and provides existential substances for animal soil organisms, microalgae and fungi as well as soil bacteria.

Since most of the starting rocks for primary rock powder are grid rocks , they promote the build-up of the clay-humus complex and improve the water retention capacity in the root space and on the soil surface. In agriculture and horticulture, this is referred to as the “crumb structure” and a quality mark for the fertility of soils (high crumb structure, high soil fertility).

Primary rock flour contributes to the enrichment of nutrients and the improvement of the water retention capacity of soils.


The application on the floor can be done dry by sprinkling or wet by adding water. The primary rock flour is then raked into the surface of the ground. The dry method is very dusty and sometimes imprecise, while the wet application binds dust and can be better dosed in a quick operation or with a stirrer. Because of their high silicate content, primary rock flour is dusted over and under leaves of susceptible crops with special devices to prevent fungal diseases. In biological plant protection against snails, aphids and caterpillars, primary rock flour is also used as a universal remedy to deter dust. However, this only works when it is dry and must be repeated as long as the animals appear in the cultures. The method of dusting is very controversial because of the pulmonary penetration of the dust and should only be carried out with a full mask and when there is no wind.

Primary rock flour can be mixed well with other substances (e.g. bentonite ) and plant manure (e.g. from nettles, field horsetail and tansy). In manure , liquid manure , manure piles, compost and compost toilet used to bind odors.

“Acid” primary rock powders are also marginally alkaline . They are not to be used for bog bed plants as they have a higher pH value that crops such as blueberries, rhododendrons , azaleas , hydrangeas , erica or camellias will not tolerate.


  • Karl Utermöhlen: The primary rock flour as a source of fertility, the foundation for building up the German people. 3rd, greatly expanded and revised edition. K. Rohm, Lorch 1934.

Web links