What is Grünkraft Calcium?
Grünkraft Calcium is a mineral foliar fertilizer based on tribomechanically activated calcite and zeolite. The product is manufactured using a sophisticated co-milling process, where calcite (calcium carbonate) and clinoptilolite zeolite are jointly processed to grain sizes below 10 micrometers. This co-milling—meaning the minerals are milled together, not separately—activates them in a way that cannot be achieved through simple mixing. The result is an electrostatically charged micro- and nano-powder that adheres to the leaf surface and penetrates directly into the plant tissue through the leaf pores.
Grünkraft Calcium is approved and registered for organic farming by EasyCert/FiBL.
Why does calcite need to be tribomechanically milled—what is the difference to normal lime powder?
This is one of the most important questions of all—because it is at the core of its effectiveness.
Conventionally milled calcite cannot be absorbed by plants—not because it is chemically incorrect, but because it is too coarse. Dr. Peter Ost, an expert in tribomechanically activated minerals and colleague of Timohir Lelas, explains it this way:
"The lime that is sometimes conventionally spread on the field is present in the field and chemically detectable, but it is not available to plants because it is too coarse. You can eat a hamburger because your mouth and the hamburger's size are roughly compatible. But if you had a football-sized hamburger, it would not be possible to eat it. And if it were 1 meter tall, then certainly not."
In the tribomechanical process, calcite particles collide at high speeds—up to three collisions per millisecond. The particles are split without destroying the internal crystal lattice structure. The result is particles smaller than 10 micrometers, which are electrostatically charged by the process.
This electrostatic charge accomplishes two things: The particles adhere optimally to the leaf surface. And they are small enough to penetrate directly into the leaf interior through the leaf pores—the stomata. And that's where the effect unfolds. More about the tribomechanical milling process versus ball mills can be found in the article:
How does Grünkraft Calcium affect the plant?
Grünkraft Calcium is dissolved in water (not really dissolved, rather well mixed. Rock cannot be dissolved) and sprayed as a fine mist onto the leaves. The particles have an average size of 8 micrometers—stomata-permeable. They penetrate directly into the leaf tissue through the leaf pores. There, the calcium carbonate decomposes:
CaCO₃ → CaO + CO₂
The released CO₂ is immediately fed into photosynthesis—the plant receives direct carbon exactly where it is needed. The released calcium oxide strengthens cell walls, regulates stomata, and activates plant-specific defense mechanisms.
Grünkraft Calcium is essentially a CO₂ fertilizer. Air contains only 0.04 percent CO₂—plants therefore chronically operate below their photosynthetic potential. Grünkraft Calcium naturally increases the CO₂ content inside the leaf and helps the plant utilize its full growth potential.
Why is zeolite in foliar fertilizer—what additional benefits does it provide?
Zeolite in foliar fertilizer has several mutually complementary functions. Dr. Peter Ost explains it this way:
"The zeolite particles can capture sunlight more strongly on the leaf, thereby contributing to a more active photosynthesis."
The ultrafine silicate particles on the leaf surface act like tiny mirrors that better distribute the incoming light and direct it into the leaf—a direct amplifying effect on photosynthesis.
At the same time, the zeolite introduces silicon into the leaf, which activates plant-specific defense enzymes—superoxide dismutase, catalase, and peroxidase—that neutralize free radicals and protect the plant against oxidative stress.
And then there's the physical protective effect: Under the microscope, the silicate particles on the leaf surface look like tiny shards of glass. Insects with sensory organs in their legs find this unpleasant and avoid the plant. The finest particles disrupt and block the respiratory organs of mites and aphids. This is not a chemical repellent—it is a purely physical process.
Why do treated leaves turn dark green—without additional nitrogen fertilizer?
This is one of the most surprising phenomena when using Grünkraft Calcium—and it has a fascinating explanation.
Calcite and zeolite on the leaf surface stimulate microorganisms that absorb ammonia directly from the atmosphere and make it available to the leaf. This supplies the leaf with natural atmospheric nitrogen—without applying additional nitrogen fertilizer.
This explains why farmers observe a more intense, richer green after treatment with Grünkraft Calcium, which looks as if the plant has been nitrogen-fertilized—even though only the mineral foliar fertilizer was applied.
Matthias W., an organic farmer from Niederfladnitz, described it this way:
"My oats were well-developed and stood like they had been nitrogen-fertilized. I also foliar-fertilized the alfalfa, and it was dark green and lush."
What is the difference between Grünkraft Calcium and conventional fertilizer?
Conventional fertilizers primarily contain the three macronutrients nitrogen, phosphorus, and potassium—NPK. They are absorbed through the soil and roots and must first be converted into plant-available forms there.
Grünkraft Calcium works on a different level. It does not stimulate nutrient supply from the outside—it activates the plant's own physiology. Through increased photosynthesis, the plant can more efficiently absorb existing nutrients from the soil. This means: Grünkraft Calcium makes the most of what is already available in the soil.
Does one still need to fertilize conventionally when using Grünkraft Calcium?
This depends on the initial state of the soil—and the answer is more nuanced than a simple yes or no.
Grünkraft Calcium promotes the development of stronger root systems—especially fine hair roots that are colonized by soil microorganisms. These microorganisms make already existing nutrients in the soil available to plants. This measurably increases the efficiency of nutrient uptake.
On well-supplied soils, conventional fertilizer use can often be significantly reduced. On depleted soils, a gradual buildup over several seasons is recommended—combined with zeolite and basalt as soil improvers and AM+PLUS microorganisms for soil life. The overarching goal is more yield with higher resource efficiency—not less yield with less effort.
Can pesticides and fungicides be reduced?
Grünkraft Calcium strengthens the plant's resistance through several mechanisms simultaneously. More stable cell walls due to calcium supply make it more difficult for fungal spores to penetrate. Well-regulated stomata reduce infection pathways. And a vital plant with a high Brix value is simply less attractive to sucking insects—because its sap is too high-quality to be utilized by simple digestive systems.
How much the need for pesticides can be reduced depends on the crop, climate, and initial situation. In European field studies, pesticide use on some experimental plots of grapevines could be reduced by up to 50 percent.
Is Grünkraft Calcium organic?
Grünkraft Calcium is based exclusively on natural minerals—calcite and clinoptilolite zeolite. It contains no synthetic active ingredients, no chemicals, and no genetically modified substances. The product is approved and registered by EasyCert in coordination with FiBL for organic farming.
What does Grünkraft Calcium have to do with water consumption?
A plant well-supplied with calcium forms denser, more stable cell walls. This reduces uncontrolled water loss through the leaf surface. At the same time, Grünkraft Calcium improves stomatal regulation—the leaf pores open and close more efficiently depending on light and temperature.
Especially in semi-arid (dry regions with little rainfall) regions or during drought stress, foliar fertilization shows a decisive advantage over soil fertilization: If the soil is dried out and nutrient availability in the soil drastically decreases, foliar fertilization reaches the plant directly—regardless of the soil condition.
University studies have shown that, for example, water savings of 19 percent were achieved in sunflowers, while biomass simultaneously increased by 13 percent. In experiments in Colombia, water savings of 33 percent were even measured. Dr. Martin Duque told us, the Steinkraft team, about this using chives. Here, the Colombian farmer had the herbs ready for export 10 days before everyone else and used less water.
What is biotic and abiotic stress—and how does Grünkraft Calcium help?
Biotic stress arises from living organisms—fungi, bacteria, insects, viruses. Abiotic stress arises from non-living factors—heat, cold, drought, flooding, UV radiation.
Grünkraft Calcium increases tolerance to both types of stress. The silicon from the contained zeolite activates plant-specific enzymes—including superoxide dismutase, catalase, and peroxidase—that neutralize free radicals and break down toxic peroxides. These enzymes are central to the plant's stress defense.
A plant that photosynthesizes intensely and is well-supplied with calcium and silicon tolerates heatwaves, dry periods, and fungal pressure significantly better than a stressed, poorly supplied plant.
What is the Brix value—and what does it have to do with Grünkraft Calcium?
The Brix value measures the density of plant sap—i.e., how many dissolved solids it contains. This includes not only sugar, but also minerals, amino acids, enzymes, and secondary plant compounds. A high Brix value therefore means not only sweet taste—it means true nutrient density.
Grünkraft Calcium measurably increases the Brix value—through more intense photosynthesis, higher mineral storage, and better cell structure of the fruits. In all cultures examined so far, field trials measured a significantly higher Brix value in treated plants compared to untreated control plots.
More about what the Brix value reveals and how to measure it yourself—in our Brix article with Reams chart and equipment recommendations.
What are the measurable effects of Grünkraft Calcium on the harvest?
From the documented field trials in Europe, Colombia, and Africa:
Higher yield—between 16 and over 50 percent for field crops, depending on the crop. Higher dry matter content in fruits—less water, more nutrients. Better storability—due to more stable cell structure and higher dry matter content. Earlier maturity—4 to 20 days earlier than untreated comparison plots, depending on the crop. More uniform fruit development—less waste, better commercial grades. Higher Brix value—measurable with a refractometer.
All field studies at a glance—in the article on Grünkraft Calcium worldwide.
How is Grünkraft Calcium applied?
Grünkraft Calcium is sprayed as an aqueous suspension onto the leaves—preferably early morning or late afternoon, when the stomata are open. Never during midday heat, strong wind, or directly before rain.
First application at 2-3 leaf stage: 5 grams per 1 liter of water. From the second application every 10-14 days: 20 to 30 grams per 1 liter of water. Water volume: 200 to 400 liters per hectare depending on crop and equipment. Wetting agent: 1 drop per 1 liter of water. Drone application: possible—recommended volume 20 to 30 liters per hectare.
Grünkraft Calcium can be easily combined with all commercially available plant protection products and fertilizers in one spray application.
What happens if I skip or miss an application?
Each application helps the plant better cope with the given conditions. If an application is not possible due to weather conditions or other reasons, it will not have a negative impact on the plant. The effect will naturally be less significant than with a fully completed program — but no harm will occur.
The application deadlines do not have to be met precisely to the hour. Small deviations do not affect product effectiveness.
What happens if I use too much Grünkraft Calcium?
This has no negative impact on the plant. A fine white film may become visible on the leaf surface — this is purely optical and will disappear with the next rain, meaning it will go into the soil. The product is not toxic and does not change the properties of other products even with overdosing.
Which crops is Grünkraft Calcium suitable for?
Grünkraft Calcium is crop-neutral — the physiological mechanism of action via the stomata works for all plants that have leaf pores.
Documented field trials are available for: grapevine, olive, sugar beet, wheat, barley, potato, lettuce, strawberry, cucumber, tomato, coffee, onion, pineapple, broccoli, corn, sugar cane, and others.
For large-scale crops such as alfalfa, corn, wheat, and potatoes, direct yield increases, earlier maturity, and reduced pesticide requirements are documented. In horticulture, as well as in citrus and mango plantations, Grünkraft Calcium improves the nutrient density of fruits, storage stability, and commercial grade.
Which Steinkraft products do you recommend for soil improvement and water retention?
For the soil, we recommend two products:
Steinkraft Zeolith BODENKRAFT PUR — tribomechanically activated clinoptilolite zeolite in 100 µm grain size for soil incorporation. It improves cation exchange capacity, retains water and nutrients in the root zone, and buffers pH fluctuations. Application: 200 kg per hectare, incorporated once annually.
Steinkraft Basalt — paramagnetic basalt meal that provides a broad spectrum of trace elements and triples the microbial soil environment through its paramagnetic properties. Application: 300 to 500 kg per hectare, up to 1,000 kg for initial application on leached soils.
Both products together form the long-term soil base — zeolite for water retention and nutrient storage, basalt for mineral supply and soil activation.
What do you recommend for drought stress and fertilization efficiency?
Two measures work together against drought stress:
In the soil: Steinkraft Zeolith BODENKRAFT PUR stores water and releases it evenly to the roots — this buffers dry periods without the plant sending stress signals.
Via the leaf: Grünkraft Calcium is particularly effective in dry periods — because it supplies the plant with CO₂ and calcium independently of soil conditions. In semi-arid regions or under drought stress, foliar fertilization is often more effective than soil fertilization.
For fertilization efficiency: Grünkraft Calcium activates more root hairs and stimulates the soil microbiome — thereby making existing soil nutrients more efficiently utilized. In many practical trials, the consumption of NPK fertilizer could be measurably reduced.
What scientific studies and field trials exist?
The scientific basis spans three continents and over twenty crops:
Europe 2011–2014: Oekomineral Group and Tribo Technologies in collaboration with SADEF laboratory and RITTMO laboratory France, as well as CIRAD Montpellier. Crops: grapevine, olive, sugar beet, wheat, barley, potato, lettuce, strawberry, cucumber, tomato.
Colombia 2017–2018: UMID Colombia S.A.S. Crops: coffee, onion, pineapple, broccoli, lettuce, corn, passion fruit, Sacha Inchi.
Africa 2026: Independent field trials with sugar cane — 46 to 49 percent more recoverable sugar with a single application four weeks before harvest.
All study results in detail — in the Global Article with all studies.
Which claims and statements are scientifically verifiable?
The following statements are verifiable through independent field studies and laboratory analyses:
- Yield increase: Yes — documented in Europe, Colombia, and Africa across more than twenty crops.
- Improvement of fruit quality: Yes — higher dry matter content, better storability, higher Brix value in all studied crops.
- Reduced pesticide requirements: Yes — documented in several European trials, especially for grapevines.
- Improved water stress protection: Yes — through improved stomatal regulation and denser cell wall structure.
- Long-term soil health: Yes — documented through zeolite and basalt as soil improvers over several seasons. CO₂/Nitrogen efficiency:
Grünkraft Calcium improves nitrogen uptake by activating ammonium absorption and natural atmospheric nitrogen supply via leaf microorganisms. A reduction in nitrogen fertilizer use is documented in practical trials — specific reduction rates depend on location and crop.
What certifications and registrations does Grünkraft Calcium have?
Grünkraft Calcium is approved and registered by EasyCert in coordination with FiBL for organic farming — confirmation is available on the product page.
For COA, SDS/MSDS, heavy metal analysis, and further certificates — please contact us directly.
Shelf life and storage conditions: Store in a dry and dark place.
How does Grünkraft Calcium differ from Grünkraft Zeolith Pur?
Grünkraft Calcium contains activated calcite with zeolite — the calcite is the carrier of the CO₂ effect and calcium for the cell walls.
Grünkraft Zeolith Pur contains exclusively activated zeolite without calcite. It forms a physical protective film on the leaf surface — ultrafine silicate particles that act as a natural repellent against sucking insects and mites while also introducing silicon into the leaf.
Both products can be combined in the same spray — and complement each other optimally: Grünkraft Calcium increases photosynthesis and nutrient density, while Grünkraft Zeolith Pur provides physical protection from the outside.
What is the complete product system for large-scale agricultural operations?
For large operations, we recommend a system of four components that act on three time scales:
Long-term — Steinkraft Basalt: Trace elements, soil structure, paramagnetic activation of the soil microbiome. Incorporated once annually.
Medium-term — Steinkraft Zeolith BODENKRAFT PUR: Water storage, nutrient retention, pH buffering. Incorporated once annually.
Short-term direct — Grünkraft Calcium: Foliar fertilization every 10 to 14 days. Direct CO₂ supply for photosynthesis, calcium for cell walls, measurable yield increase.
Supplementary — AM+PLUS Active Microorganisms: Stock solution made from Austrian organic herbs. Activates the soil microbiome, makes minerals available to plants, ferments instead of putrefies.
This system closes all relevant gaps: soil, leaf, water, microorganisms — and is suitable for drone application in large-scale use.
For advice on specific crops, climate zones, and farm sizes — please contact us.
What do farmers report from practice?
Matthias W., organic farmer, Niederfladnitz:
"The most important thing is to get through the dry phases, and the foliar fertilizer was really good at supporting that. There was little rainfall this year, and yet I have very vital plant stands. My oats developed well and stood as if nitrogen-fertilized. The alfalfa was dark green and lush. I was able to sell my green manure as feed well."
Farthofer Distillery, Öhling:
"This year, I used GRÜNKRAFT Blatt for my malting barley for the first time and am very satisfied with the harvest result. We applied GRÜNKRAFT at the 2-leaf and 4-leaf stages, and the difference to competitors' fields is clearly visible. Through this measure, we really obtained a large, strong grain of good, dry quality."
All products for the garden in our Garden Collection and for agriculture in our Agriculture Collection.
Grünkraft Calcium directly — to the product page.
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