Hemp is experiencing a renaissance in Austria. After decades of stigmatization and prohibition, it is returning to local fields — as a fiber plant, an oil supplier, a source of CBD, and a valuable link in crop rotation (the sequence of different crops on the same land for soil improvement).
And it deserves this renaissance. Hemp is an extraordinary crop. It suppresses weeds with its dense growth. It requires hardly any pesticides. It improves the soil through its deep root system. It provides significant amounts of biomass in a single season.
But hemp is more demanding than its reputation as a "low-maintenance plant" would suggest. What it produces from the soil and air depends directly on how well it is cared for. And this determines not only the yield — but also the quality. The CBD content. The fiber quality. Everything for which the farmer markets their harvest.
What hemp really needs — the basics
Soil: Hemp loves light, warm, well-aerated soils. It does not tolerate waterlogging (standing water in the soil) or soil compaction (hard, difficult-to-penetrate soil layers) — these inhibit root growth and open the door to root rot and Fusarium (soil-borne fungal pathogens).
pH value: Neutral to slightly alkaline — between 6.5 and 7.5. This is the range in which all important minerals are optimally available. Soil that is too acidic blocks calcium absorption — and calcium is particularly important for the hemp plant.
Nitrogen: Hemp has a comparatively high nitrogen requirement — but excessive nitrogen fertilization promotes excessive vegetative (leaf- and stem-oriented) growth at the expense of quality. The key is efficiency — how well does the plant utilize the available nitrogen?
Calcium: This is one of the most underestimated levers in hemp cultivation. Calcium is the key that unlocks all other minerals — it regulates the transport of nutrients into the plant cell, strengthens cell walls, and activates photosynthesis. A hemp plant that is well-supplied with calcium processes all other nutrients more efficiently.
CBD — a secondary plant compound that needs photosynthesis
Here lies the most scientifically fascinating argument for intensive plant care in industrial hemp.
CBD (cannabidiol) is a secondary plant compound (a protective and active substance that the plant produces itself). Scientific research shows that the production of cannabinoids as secondary metabolites in hemp — including CBD — is linked to the plant's stress defense. The plant produces CBD as a protective response against UV radiation, pests, and other stress factors.
This is the same principle we know from other secondary plant compounds: quercetin in red onions, lycopene in tomatoes, sulforaphane in broccoli, resveratrol in grapevines. All these substances are created when the plant is vital, conducts photosynthesis intensively, and is well-supplied with minerals.
This means: A hemp plant that conducts more photosynthesis — because it is supplied with CO₂ directly via the leaf — has more energy for the formation of secondary plant compounds. More energy potentially means more CBD, more terpenes (aromatic compounds that give the hemp plant its characteristic scent and taste), more of everything that defines the quality of the harvest.
This is the CBD-photosynthesis connection. And it is the same mechanism that leads to more polyphenols in grapevines, more lycopene in tomatoes, and more allicin in garlic.
Hemp as a C3 plant — why foliar fertilization is particularly effective
Hemp is a C3 plant (a plant that processes CO₂ via the so-called Calvin cycle, where the CO₂ concentration in the leaf directly determines the rate of photosynthesis). This means: The photosynthesis of hemp is directly dependent on the availability of CO₂ inside the leaf.
The atmosphere contains only 0.04 percent CO₂ — that is too little for maximum photosynthetic activity. Grünkraft Calcium and HANFKRAFT deliver CO₂ directly into the leaf interior — through tribomechanically activated calcite particles (calcium carbonate particles activated by a high-speed process) that penetrate through the leaf pores and release calcium and CO₂ there.
The result: The hemp plant's photosynthesis engine runs at full speed — regardless of what is happening in the outside air. More photosynthesis. More energy. More biomass. Potentially more CBD.
The complete program for vital industrial hemp
Step 1 — pH regulation: BODENKRAFT Carbonate Lime
Timing: Before sowing — ideally in the autumn before or early spring.
Hemp needs a pH value between 6.5 and 7.5. Many Austrian arable soils — especially after intensive cultivation — are too acidic. Soil that is too acidic blocks the absorption of calcium, phosphorus, and trace elements — even if these nutrients are present in the soil.
BODENKRAFT Carbonate Lime is tribomechanically activated calcium carbonate lime from Upper Austrian mining with a soil reactivity (effectiveness in the soil) of over 90 percent. Conventional lime only achieves about 50 percent soil reactivity — and must therefore be applied in four to six times the quantity.
Application: 400 to 600 kg per hectare, incorporated once a year.
Step 2 — Soil structure: BODENKRAFT PUR Zeolite
Timing: Before sowing, simultaneously with the lime.
Hemp does not tolerate waterlogging or soil compaction. Steinkraft Zeolite BODENKRAFT PUR improves water retention (water storage capacity) and drainage (water runoff in the soil) at the same time — it stores moisture during dry phases and prevents waterlogging during rain. In addition, it improves the cation exchange capacity (the soil's ability to bind nutrients) and keeps calcium and nutrients in the root zone.
Application: 300–400 kg per hectare, incorporated.
Step 3 — Activating soil life: AM+PLUS Microorganisms
Timing: At sowing — and every 3 to 4 weeks thereafter.
AM+PLUS is the original solution made from Austrian organic herbs, based on lactic acid bacteria (microorganisms that promote fermentative rather than putrefactive processes in the soil).
For hemp, the soil microbiome (the community of beneficial microorganisms in the soil) is particularly important — active soil life makes minerals plant-available that remain bound without biological activity. Additionally, a vibrant soil microbiome keeps soil-borne fungal pathogens like Fusarium in check.
Application: As a soil drench at sowing, then every 3 to 4 weeks.
Step 4 — Foliar fertilization: GRÜNKRAFT Calcium from the 2-3 leaf stage
Timing: As soon as the first true leaves appear — starting early is crucial.
For field operations, we recommend GRÜNKRAFT Calcium — tribomechanically activated calcite with zeolite in the proven field formulation. The particles are smaller than 10 micrometers (stomata-compatible — small enough to penetrate through the leaf pores into the leaf interior). There, the calcium carbonate decomposes into CO₂ for photosynthesis and calcium oxide for the cell walls.
GRÜNKRAFT Calcium can be easily combined with all standard plant protection products and fertilizers in a single spraying.
First application at 2-3 leaf stage: 2 kg per hectare. From the second application every 10–14 days: 3 kg per hectare. Water volume: 200–400 liters per hectare depending on equipment. Drone application: possible — recommended volume 20–30 liters per hectare. Spraying time: Early morning or late afternoon, when the stomata (leaf pores) are open.
For smaller areas and hobby cultivation, HANFKRAFT is available in the practical 650g unit — specially formulated for hemp and cannabis plants and ideal for up to 200 plants with 3 applications.
What distinguishes hemp from other crops — and why that matters
Hemp is an exceptionally fast-growing, heavy-feeding plant (a plant that requires many nutrients for its rapid growth). In a single season, it draws significant amounts of calcium, magnesium, potassium, and trace elements from the soil. What it removes must be returned — otherwise, the soil will become depleted with every season.
On one hand, this makes hemp a valuable link in crop rotation — it loosens the soil with its deep roots and leaves behind organic matter. On the other hand, it needs good soil itself to reach its full potential.
Those who grow hemp for several years on the same or adjacent areas and simultaneously build up the soil with zeolite, basalt, and microorganisms will observe better results with each season — because the soil performs better every year.
What farmers observe in practice
Farmers who use HANFKRAFT or Grünkraft Calcium on industrial hemp consistently report:
Stronger, more stable plants that do not lodge (fall over) even in storms and wind. More uniform development over the entire vegetation period (growth period). More intense leaf color — the dark green that indicates good nitrogen utilization and intensive chlorophyll formation. Less pest pressure — especially fewer aphids, which preferentially infest weak, poorly nourished plants.
The complete program at a glance
| Phase | Measure | Product | Timing |
|---|---|---|---|
| Before sowing | Regulate pH | BODENKRAFT Carbonate Lime 400–600 kg/ha | Autumn or spring |
| Before sowing | Improve soil structure | BODENKRAFT PUR 300–400 kg/ha | Simultaneously with lime |
| At sowing | Activate soil life | AM+PLUS | At sowing |
| 2-3 leaf stage | First foliar fertilization | GRÜNKRAFT Calcium 2 kg/ha | As soon as leaves appear |
| Growth phase | Foliar fertilization continued | GRÜNKRAFT Calcium 3 kg/ha | Every 10–14 days |
| Entire vegetation period | Maintain soil life | AM+PLUS | Every 3–4 weeks |
All products for hemp cultivation in our Agriculture collection.
GRÜNKRAFT Calcium direct — to the product page.
HANFKRAFT for smaller areas and hobby cultivation — to the product page.
What CBD as a secondary plant compound has to do with photosynthesis — in the photosynthesis article.
Why soil health determines the quality of every harvest — in the article about minerals and degraded soils.
When to use foliar fertilization and when to use soil fertilization — the big comparison.
Sources: Chamber of Agriculture Upper Austria, Organic Hemp Cultivation Guidelines | Nativ Canna, Hemp cultivation in Austria | BioBloom, CBD and industrial hemp in Austria | BioRxiv, Foliar gas exchange and cannabinoid contents of hemp varieties, Texas 2025
