Rock dust has become indispensable in many hobby and home gardens. The mineral material can be used for many purposes and is a good substitute for synthetic products. In this article you will find out what rock dust is and how to use it.

Primary rock flour is a soil additive

Table of Contents

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  1. the essentials in brief
  2. What is bedrock meal?
  3. application and dosage
  4. Buy bedrock meal
  5. frequently asked Questions

    6. the essentials in brief

    • There are different types of primary rock flour, which consist of different original rocks and therefore differ in pH and in their nutrient composition.
    • Primary rock flour can be used in many ways and is suitable for supplying plants with minerals, for soil improvement, for improved composting or for pest control.
    • Which primary rock flour you can use depends on the desired use as well as on your garden soil, its composition and pH value.
    • Rock flour (€14.13) can be applied dry or wet, for example dissolved in water or a plant manure.

    What is bedrock meal?

    Primary rock flour, also known as rock or stone flour, is basically nothing more than very finely ground rock. It is mostly extracted from basalt or other lava rocks and mostly contains silica and aluminum oxide. In addition, depending on the starting material used, the powder is more or less rich in minerals and trace elements. For this reason, gardeners like to use rock flour as a soil activator, as the material enriches the soil with trace elements, improves soil life and thus ensures a higher humus content.

    The high proportion of silicic acid in turn makes plants treated with it more resistant to plant diseases (especially fungal diseases) and pests. Furthermore, direct treatment of the plants with rock flour - for example by dusting - prevents various harmful insects from settling. Prehistoric rock flour has been used successfully against the box tree moth for years. Despite a certain fertilizing effect, this agent is not a fertiliser, but merely a so-called soil additive.

    All commercially available primary rock flours lack the essential main nutrients, so that these products are not suitable as the sole or main fertilizer used.

    composition and ingredients

    Prehistoric rock powder can consist of different stones, which is why the color varies from almost white to gray to brown

    In order to obtain rock flour, the massive source rock is first mined in quarries. For this purpose, lava stones such as basalt or diabase are mainly used in the garden because they have a particularly high mineral content. The material is then broken up into small pieces and ground into a very fine flour in a rock mill. Larger rock components are finally sieved out. This process consumes large amounts of energy.

    In addition to lava stones, these types of rock are also used for primary rock and stone powder:

    • sand-lime brick
    • quartz
    • granite
    • zeolite
    • bentonite and other clay powders

    The specific ingredients and thus the possible uses of a primary rock meal depend largely on which rock type(s) were used for the product. Typically, however, all stone flours contain minerals and trace elements such as

    • Iron (lava flour is particularly rich in iron)
    • magnesium
    • calcium
    • potassium
    • silica
    • manganese
    • and molybdenum

    in different compositions. Although bentonite and other clay powders also belong to the primary rock powders, their properties differ quite significantly from other products, such as those based on volcanic origin. These agents are primarily used to increase the storage capacity of the soil and thus prepare it for the absorption of water and nutrients.

    effect

    Basically, earth is nothing more than a mixture of weathered rock and decayed organic remains. Thus, the garden soil naturally contains all the nutrients that plants need for healthy growth. Depending on the type and composition, however, soils differ in their nutrient content, which is why you can use products such as rock flour to improve the soil according to the needs of the plants growing on it:

    • sandy soils: are often low in nutrients because the rainwater grows out the nutrients it contains and the humus content is also low. Here, primary rock flour improves the nutrient content.
    • Loam and clay soils: are often heavy and not very permeable to water. Here, the primary rock flour should ensure more looseness and improved humus formation.
    • Acid garden soil: are only suitable for a few garden plants, as most plants do best in neutral to slightly alkaline soil. An alkaline primary rock flour helps here, which raises the low pH value and thus neutralizes it.

    Incidentally, the various primary rock flours not only differ in their composition, but also in their pH value. This depends very much on how high the calcium content is - the more calcium stone powder contains, the more alkaline it is in its effect. Thus, the pH value of the garden soil can also be regulated with the help of a suitable primary rock powder.

    Advantages over artificial mineral fertilizers

    Synthetic fertilizers have many disadvantages

    “Prime rock flour is not a fertilizer, but a soil additive. As a result, you cannot use it to correct nutrient deficiencies!”

    As a rule, primary rock meal is intended to replace synthetic mineral fertilizers. In fact, these are problematic from an ecological point of view:

    • The production of mineral fertilizers happens in mining, which is why landscapes are destroyed.
    • The processing of the mined material requires a large amount of chemicals, some of which are toxic, and is very energy-intensive.
    • The production of nitrogen fertilizers in particular is problematic in this respect.
    • These consume a lot of energy and also produce a lot of fine dust.
    • In addition, greenhouse gases that are harmful to the climate, e.g. B. nitrous oxide released.
    • With synthetic fertilizers, the risk of over-fertilization of the soil is very high.
    • As a result, excess fertilizer ends up in the natural water cycle or in the groundwater.
    • Nitrogen, for example, combines with oxygen to form nitrate, which in turn accumulates in plants and reduces the oxygen content in water.

    Of course, even primary rock dust is not necessarily ecological in terms of its production, which is why you should use the agent as sparingly as possible and replace it with other materials. Particularly good fertilizers, which contain a large number of natural nutrients and with which over-fertilization is practically impossible, are of organic nature. This primarily includes compost, composted / rotted manure, mulch and horn shavings (€32.93) or horn meal.

    digression

    Does bedrock powder also have disadvantages?

    In organic farming, primary rock flour from lava rock is used as a natural mineral fertilizer. Although this product is of natural origin and by using it you avoid the sometimes serious disadvantages of synthetic fertilizers, the rock flour is not really sustainable either. The stones used are mined in quarries, which destroys entire landscapes. This does not necessarily happen in Germany, but often far away - so that the CO2 required for transport must be added to the destruction of the landscape.

    Application and dosage of primary rock flour

    Primary rock flour is very versatile in use. Depending on the starting material used, there are various possible uses in the garden. We have summarized for you in this section what these are and how to dose the material correctly.

    Various types of primary rock dust

    Primary rock powder consists of different parent rocks. In this section we have put together for you which rock is best used in the garden.

    parent rock main ingredients application areas
    basalt Iron, magnesium, many minerals and trace elements Supply of minerals and trace elements, increase of microbiotic activity in the soil and in the compost
    diabase Iron, magnesium, many minerals and trace elements, as well as calcium Supply of minerals and trace elements, increase in microbiotic activity in the soil and in the compost, acidification of strongly alkaline soils
    granite lower mineral content Increase in microbiotic activity in the soil and in the compost, acidification of strongly alkaline soils
    bentonite volume Improvement of the storage capacity, improvement of the clay-humus ratio, especially for sandy soils
    zeolite lower mineral content Improvement of the storage capacity of water and nutrients, strongly alkaline effect

    Incidentally, there is an important reason why the primary rock flour is so finely ground: only the fine degree of grinding ensures that the minerals contained are dissolved in the water and can then be absorbed by the plants via the roots. However, it is essential to pay attention to the pH value of the product, since a strongly alkaline material (e.g. zeolite flour) has a major impact on the soil - at pH values of more than 8, however, plants only poorly absorb the soil nutrients and develop growth disorders.

    tips

    When caring for heavy-consuming plants such as tomatoes and lawns, you should use lava flour, as this contains the highest proportion of micronutrients.

    Application in the garden

    Primary rock flour can be sprinkled directly onto the bed and then worked into it

    Rock dust can either be spread and worked into the soil or dissolved in liquids (e.g. irrigation water or plant manure) and applied in this way. The material is also very well suited to stimulating microbial life in the compost and thus accelerating the decomposition of the organic material - quite apart from the fact that the nutrients contained in the rock flour are also added to the compost and thus enrich it with minerals.

    Rock flour not working? These are the reasons

    Many a gardener has already tried rock flour and was unable to record any positive effects. This can have different reasons:

    • the wrong / unsuitable rock flour was used (see buying tips)
    • the duration of treatment was too short
    • the amount used is too small
    • the plants supplied with it have not absorbed the material

    In principle, not all garden plants react equally positively to the addition of rock dust. However, the product is particularly effective in fruit and berry trees and in vegetable cultivation. However, to ensure that the yields remain consistently high, you should apply the rock flour every year. It is not taken up by the plant roots until it is completely decomposed. Incidentally, this is also the reason why a one or two-time application shows no effect.

    tips

    Since primary rock flour can only be absorbed by plants very slowly, it is not suitable for short-term remedying a possible lack of minerals or trace elements. The effect of the remedy is more long-term.

    Rock dust in pest control

    In addition, the primary rock flour also serves well in pest control. To do this, you can dust the endangered plants - such as box or apple trees - directly with the powder. Choose a dry, windless day and be sure to wear a respirator so you don't inhale the fine flour. However, the application must be repeated regularly, especially after a downpour.

    How to use bedrock dust correctly in the garden

    So that the fine powder does not fly away, the soil should be watered before and after discharge

    There are two ways of spreading the rock flour: dry or wet. We will explain how this works here.

    For dry application, it is best to proceed as follows:

    1. A windless, dry day in spring or late autumn is ideal.
    2. However, the soil should be well moistened so that the fine dust does not blow away.
    3. Now apply the primary rock flour directly to the beds.
    4. Be sure to wear mouth and respiratory protection!
    5. Work it into the ground with a hoe.
    6. The material should be about an inch to two inches below the ground, as this is where the roots absorb it best.

    As an alternative or in addition, you can spread the primary rock flour directly between the rows of vegetables during the growing season. Here it helps, applied thickly, among other things against hungry snails.

    When used wet, simply add the primary rock flour to the irrigation water or to a prepared plant manure. The latter also has the advantage that the brew smells much less - the stone flour binds the unpleasant smell.

    tips

    Berry bushes and strawberries can be supplied with minerals by spreading the primary rock powder directly into the root area of the plants and then pouring it vigorously.

    Dose rock flour correctly

    How much rock flour you use in your garden depends on various factors.

    • Composition and pH of the soil: In principle, the lower the pH value of the soil, the more rock dust is required. While you need about 150 grams per square meter on calcareous soils, up to 300 grams per square meter are recommended on acidic soils.
    • composition of the product: The amount of rock flour needed also depends on the composition and pH of the selected product. Appropriate dosage recommendations - usually broken down by soil type - can be found printed on the packaging.
    • treated plants: In addition, the amount of stone dust used also depends on which plants you want to treat with it. Typical moor bed plants such as rhododendrons, for example, may only get very little, while lime-tolerant and heavily consuming plants - which own many vegetables - can tolerate and also need much more.

    Ultimately, the dosage depends primarily on the manufacturer's recommendation. Be sure to comply with these and also measure the pH of the soil before use to avoid possible overdoses.

    Can humans and animals also ingest rock meal?

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    Many resourceful manufacturers offer rock dust not only for the garden, but also for human consumption. Supposedly, if eaten regularly, nutrient deficiencies could be avoided. However, that's nonsense, because if you eat a healthy and varied diet, you already get the necessary minerals and trace elements with your food.

    Furthermore, the line between "healthy" and "toxic" is very narrow, especially with these micronutrients, since the body only needs very little of them. An overdose, as it inevitably happens when taking rock flour internally, always has negative health consequences - no matter what enterprising companies and influencers claim. Just eat more organic vegetables and fruit from your own garden, it's not only healthier, it also tastes better.

    Buy rock flour - you should pay attention to this

    When buying rock flour, you should definitely keep your eyes open and study the composition of the desired product intensively: Strictly speaking, the low-priced rock flour from the discounter or the garden center is not. The designation "rock flour" - with and without an "Ur" in front of it - is not legally protected and can therefore be used for various rock flours or mixtures. Many of these "primeval rock flours" contain a large proportion of lime or sand-lime brick and ground sand - however, both components are not primary rocks in the sense of the definition. Although lime is also practical in the garden, it is not suitable for many of the uses attributed to real rock dust.

    Even primary rock flour obtained from granite and feldspar is not necessarily suitable for soil improvement, since both consist to a large extent of silicon dioxide - this is the main component of sand and is therefore worthless as a fertilizer or compost booster. Stone flour made from quartz or zeolite also contains more sand than nutrients. Although the products mentioned are not particularly rich in minerals and trace elements, they can still be used to loosen loamy and heavy soils. Instead, make sure to buy primary rock flour made from lava rocks or simply lava litter.However, this should not consist of black, glassy lava, since this material also contains mainly silicates. Porous, brown lava is best suited. This is very absorbent, stores water and nutrients. Therefore, it is suitable for soil improvement purposes.

    frequently asked Questions

    How do I know what pH my soil has?

    The pH value of the soil can be determined with a simple test from the pharmacy or garden center. All you need is test strips, which you hold in a soil sample mixed with water (be sure to follow the manufacturer's instructions!) and then use the discoloration to determine whether the soil is alkaline or acidic.

    Now you can select the right primary rock flour: For alkaline soil, use one with a rather acidic pH value, for acidic soil, on the other hand, use a product with a basic pH value. However, you do not have to measure the pH value of the primary rock flour, as this is usually printed on the product packaging.

    How much does bedrock meal cost?

    The prices for primary rock flour vary greatly and depend on which specific product is to be purchased in which package size. Basically, there are cheap offers up to expensive suppliers, whereby the price often reflects the composition of the primary rock powder. Cheap primary rock flour often contains a large proportion of limestone and sand, which is why, strictly speaking, it is not primary rock.

    Bedrock flour is often sold in a 25-kilogram sack, which costs between around 15 and 30 euros, depending on the manufacturer. The smaller pack sizes - usually five or ten kilograms - are usually more expensive per kilo than the large packs. Since rock flour cannot spoil if it is kept dry, it is worth buying larger quantities - especially since you tend to use more rather than less. If rock dust is to work, you have to use quite a bit of it.

    What alternatives are there to bedrock flour?

    Depending on the area of application, you have various alternatives. For example, compost or rotted manure are also very suitable for soil improvement, especially since these substances can also be used as fertilizer - for which primary rock dust is not suitable. Acidic soils, on the other hand, benefit from the use of natural lime, which raises the low pH value and thus promotes plant growth. Coffee grounds also act as a soil conditioner, at least when the pH of the garden soil is too high.

    When it comes to pest control, you can also rely on lime, especially algae lime. This has been used successfully for years against harmful butterflies such as the box tree moth. Homemade plant manure and broths, such as those made from stinging nettles, tansy, garlic or horsetail, also help against other common garden pests and fungal diseases. As you can see, ecological and non-toxic cultivation of the garden is possible even without expensive primary rock flour.

    tips

    When liming the lawn, you can use a mixture of garden lime (9.70€) and primary rock dust and thus fertilize the green area with additional minerals.

Category:

Garden design