A red onion that is still firm and fresh a week after harvesting. An onion that tastes like onion — intense, spicy, mineral. Packed with Quercetin and Anthocyanins, the most valuable phytochemicals a red onion has to offer.
This is no coincidence. It's the result of a well-thought-out system that starts with the soil — long before the first onion seedling goes into the ground. And my sister insists that we only plant red onions anymore.
Why a red onion from healthy soil contains more quercetin and anthocyanins than one from the supermarket — and what the Brix value has to do with it — we explain in detail in our article on nutrient-rich foods.
And all the products we explain here can be found in our shop in the Gardening Corner - Homegardening and the large containers in the Agriculture category
This guide shows step-by-step how to grow nutrient-rich red onions — on large farms with hectares of land for our vegetable growers and in the garden with 20 plants in raised beds or wherever.
Why the system decides — not the individual product
Anyone who simply sprays Grünkraft Calcium already sees a significant effect — field studies from Colombia show over 50 percent more yield from foliar fertilization alone. But those who apply the complete system achieve more: not only higher yields, but true nutrient density. More dry matter. More minerals in the onion. A measurably higher Brix value. And in red onions — more quercetin, more anthocyanins, more of exactly what makes these onions so special.
The system works on three time levels simultaneously:
Long-term — Steinkraft Basalt builds up the soil over years and continuously releases minerals. Its paramagnetic properties activate the entire soil life.
Medium-term — Steinkraft Zeolith stores water and nutrients and releases them to the plant roots as needed.
Immediate effect — Grünkraft Calcium acts directly on the leaf, immediately supplying the plant with CO₂ and calcium for photosynthesis.
AM+PLUS Active Microorganisms connect all three levels: They make minerals available to plants, fermentatively break down organic matter, and build true microbial diversity in the soil. And provide diversity at an energetic level: over 200 plants and minerals.
Step 1 — Soil Preparation: Incorporate Steinkraft Zeolith
Timing: 2 to 4 weeks before planting.
Zeolith is a natural volcanic mineral with a unique lattice structure — the best natural ion exchanger in the soil. It absorbs ammonium, potassium, calcium, and other nutrients and slowly releases them to the plant roots as needed. Less leaching by rain. More nutrients exactly where the roots need them.
Particularly important for red onions: Zeolith regulates the soil's pH value to the optimal range between 6.0 and 7.0. Only in this range are calcium, phosphorus, and potassium maximally available — and only a red onion well supplied with calcium produces the full amounts of quercetin and anthocyanins.
Zeolith also offers AM+PLUS microorganisms an ideal habitat: The lattice structure protects them, keeps them active, and gives them support in the soil matrix.
Application in the field: 300-400 kg of Zeolith per hectare, incorporated directly during plowing or harrowing. Once per season, 1 to 2 times annually.
Step 2 — The Paramagnetic Soil Activator: Steinkraft Basalt
Timing: Simultaneously with Zeolith
Steinkraft Basalt is not ordinary rock dust. It possesses very high paramagnetic properties — and this makes a decisive difference for the entire soil life.
In the 1970s and 1980s, researcher Philip S. Callahan systematically investigated why some soils are so extraordinarily productive. His finding: The most fertile soils in the world — including the legendary Irish basalt soils — have a high paramagnetic charge. Paramagnetic soils react to the natural Earth's magnetic field and transmit its energy into the root zone. This stimulates plant growth and soil health in a way that cannot be explained purely chemically.
And here lies the special synergistic effect of Steinkraft Basalt and AM+PLUS: Paramagnetic soils not only activate microorganisms — they triple the microbial environment. Three times more active microorganisms in the soil mean three times more nutrient mobilization, three times more humus buildup, three times more plant health.
Additionally, Steinkraft Basalt provides a broad spectrum of trace elements — silicon, iron, manganese, copper, zinc, cobalt, molybdenum — which are missing in depleted soils and which a red onion with high nutrient density needs. It improves soil structure, inhibits rotting processes, and binds CO₂ from the atmosphere.
Application in the field: 300 to 500 kg of Basalt per hectare, spread on the soil and worked in. When converting to regenerative farming, up to 1,000 kg per hectare in the first year.
Step 3 — Build Soil Life: AM+PLUS Active Microorganisms
Timing: At or shortly after planting — and then regularly during vegetation.
Steinkraft AM+PLUS is not an ordinary microorganism solution. This original solution is made from Austrian organic herbs, based on lactic acid bacteria, refined with homeopathy and spagyrics. The result is an extraordinarily living, diverse microorganism community of bacteria, fungi, yeasts, actinomycetes, and protozoa — regional and thus perfectly adapted to Central European soil conditions.
What these microorganisms achieve in the soil is remarkable: They promote fermentative processes instead of rotting. They mobilize nutrients and make them available to plants — even minerals that are already present in the soil but cannot be absorbed without microbial help. They build humus, stabilize soil structure, and improve water retention capacity.
For red onions, the symbiosis with mycorrhizal fungi, which are contained in AM+PLUS, is particularly valuable: These fungi envelop the onion root with an invisible network that increases the effective root surface many times over. This allows the onion to reach minerals and trace elements from soil areas that its own root would never reach.
Customers report: Working with Basalt, Zeolith, and AM+PLUS together, already in the third year, slug-free — the orange slugs simply stay away.
Application in the field: As a soil drench during planting, then every 3 to 4 weeks as a foliar spray or soil drench during vegetation. Dose according to manufacturer's recommendation — AM+PLUS is highly concentrated and requires significantly less quantity per hectare than conventional products.
Why microorganisms are better than any organic fertilizer — this blog article explains it.
Step 4 — First Foliar Fertilization: Grünkraft Calcium at the Young Plant Stage
Timing: As soon as the first true leaves appear.
Studies from France and Colombia are clear: The earlier the first treatment begins, the stronger the overall effect. Young leaves have particularly active, well-opened stomata. The calcite particles penetrate particularly effectively, decompose in the leaf, and immediately provide CO₂ and calcium for photosynthesis.
Grünkraft Calcium can be easily applied together with all other plant protection products, fungicides, and fertilizers in one spray — which significantly simplifies application in daily operations. Of course, also with AM+PLUS.
Concentration: 0.3% solution — 3 grams of Grünkraft Calcium powder per liter of water. First, dissolve the powder well in a small amount of water (although it doesn't dissolve, it's rock, super fine) in the sense of mixing it well with water. Then top up.
Spray as a fine mist over the entire leaf surface — early morning or late afternoon, not in strong winds and not in the midday heat.
Step 5 — The Repetition Scheme
Interval: Every 14 to 20 days throughout the entire growing season.
Regularity is the decisive factor. Grünkraft Calcium does not act as a one-time cure — it acts as a continuous supply. Each application renews the CO₂ supply in the leaf, strengthens cell walls, and extends the active vegetation cycle.
Recommended program for red onions:
Treatment 1 — Young plant stage, first true leaves: 0.3% concentration. Treatment 2 — 14 to 20 days later, active growth phase: 0.3% concentration. Treatment 3 — When the onion begins to form: 0.5% concentration. Treatment 4 — Onion filling phase: 0.5% concentration.
In case of stress due to drought, heavy rain, or strong temperature fluctuations: Immediately increase frequency. During stress phases, the plant particularly needs calcium for stomatal regulation and CO₂ for photosynthesis.
Quantity required: 2 to 3 kg of Grünkraft Calcium per hectare per season.
For the garden: 20 red onion plants in the bed
Those who don't cultivate hectares, but rather 20 red onions in the garden or raised bed, can implement the same program on a small scale — with small package sizes specifically designed for this purpose.
Soil preparation: Work Steinkraft Zeolith and Steinkraft Basalt granules well into the bed soil — about a handful of each product per square meter, mixed 5 to 10 cm deep. This can be done easily with a rake or when turning over the bed.
AM+PLUS Active Microorganisms: When planting the young plants, water the root zone with diluted AM+PLUS solution — a splash of AM+PLUS to a watering can of water. Then repeat weekly, either as a drench directly to the roots or as a fine spray on leaves and soil.
Grünkraft Calcium: Mix a small spray bottle with 0.3% solution — that's 1.5 grams of powder to 500 ml of water. As soon as the first true leaves appear, finely spray over the leaves every two weeks. For 20 onion plants, a short spray session of a few minutes is sufficient. Grünkraft Calcium can be easily sprayed together with other plant care products.
What you will observe in the garden: Just a few days after the first Grünkraft Calcium application, the leaves will visibly become darker and a more vibrant green. The red onions will develop more evenly, and the shoots will become more robust. At the end of the season: significantly heavier onions with more intense color and longer shelf life in the refrigerator, and much more of the important nutrients.
Measuring Nutrients
If you really want to measure how much nutrient density is in your red onions, you can do so with a simple digital refractometer. Simply put a few drops of onion juice on the device — results in seconds. The comparison is astounding: a red onion from the supermarket often has 4 to 5 °Brix. A red onion from healthy soil with mineral foliar fertilization can reach 8 to 12 °Brix — that's double the nutrient density, double the taste, double the shelf life.
And that's not just a number. A high Brix value in red onions specifically means: more quercetin and more anthocyanins — precisely the substances that give red onions their intense color and extraordinary health benefits. Quercetin has anti-inflammatory effects, strengthens the immune system, and protects the heart. Anthocyanins protect against oxidative stress and are associated with up to a 32 percent lower risk of heart attack. A plant that undergoes intense photosynthesis — exactly what Grünkraft Calcium achieves — simply has more energy to form these valuable secondary plant compounds. The more nutrient-rich onion is therefore also the healthier, tastier, and longer-lasting one.
If you grow a treated row next to an untreated one in your own garden and measure both on harvest day, you will see the difference in black and white.
What happens in the red onion
When Grünkraft Calcium is sprayed on the leaf, the micro-particles penetrate through the stomata. That's why it's important for the powder to be fine enough to be absorbed by the stomata. And there, the calcium carbonate decomposes:
CaCO₃ → CaO + CO₂
The CO₂ is immediately fed into photosynthesis — the plant gets direct carbon for sugar production. Calcium oxide strengthens the cell walls, regulates stomata, activates defense mechanisms against fungal diseases, and promotes nitrogen uptake.
The result for red onions is particularly valuable: More photosynthesis means more sugar in the onion — and more sugar means more energy for the formation of quercetin and anthocyanins, the secondary plant compounds that give the red onion its color and health benefits. An onion that undergoes a lot of photosynthesis is automatically a more nutrient-rich onion.
The results at a glance
From field studies with activated calcite - Grünkraft Calcium - as foliar fertilization:
Weight per onion: +44.8 percent — from 71 grams to 125 grams.
Productivity: +53.58 percent.
Economic gain: +60 percent.
Shelf life: significantly improved due to higher dry matter content.
Resistance to climate stress: measurably higher.
The complete program at a glance
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Before planting |
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