Hemp is experiencing a renaissance in Austria. After decades of stigmatization and prohibition, it is returning to domestic fields – as a fiber crop, an oil source, a CBD source, and a valuable component in crop rotation (the sequence of different crops on the same area to improve soil).
And it deserves this renaissance. Hemp is an extraordinary crop. It suppresses weeds due to its dense growth. It requires hardly any pesticides. It improves the soil through its deep root system. It yields significant biomass quantities in a single season.
However, hemp is more demanding than its reputation as a "low-maintenance plant" suggests. What it produces from the soil and air directly depends on how well it is cared for. And this not only determines the yield but also the quality. The CBD content. The fiber quality. Everything for which the farmer markets their harvest.
What Hemp Truly Needs — The Basics
Soil: Hemp loves light, warm, well-aerated soils. It does not tolerate waterlogging (standing water in the soil) and soil compaction (hard, difficult-to-penetrate soil layers) – these inhibit root growth and open the door for 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 uptake – 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-focused) growth at the expense of quality. The key is efficiency – how well does the plant utilize the available nitrogen?
Calcium: Here lies one of the most underestimated factors in hemp cultivation. Calcium is the key to 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 requires 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 produced by the plant itself). Scientific research shows that the production of cannabinoids as secondary metabolites in hemp – including CBD – is linked to the plant's stress protection. The plant produces CBD as a protective reaction 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 produced when the plant is vital, actively photosynthesizes, and is well supplied with minerals.
This means: A hemp plant that photosynthesizes more – because it is supplied with CO₂ directly through the leaf – has more energy for the formation of secondary plant compounds. More energy potentially means more CBD, more terpenes (aromatic compounds that make up the characteristic scent and taste of the hemp plant), more of everything that defines the quality of the harvest.
This is the CBD-photosynthesis connection. And it's 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 Calvin cycle, where CO₂ concentration in the leaf directly determines the rate of photosynthesis). This means: Hemp's photosynthesis is directly dependent on the availability of CO₂ inside the leaf.
The atmosphere contains only 0.04 percent CO₂ – which is too little for maximum photosynthetic activity. Grünkraft Calcium and HANFKRAFT deliver CO₂ directly into the leaf interior – through tribomechanically activated calcite particles (limestone particles activated by a high-speed process) which penetrate the leaf pores and release calcium and CO₂ there.
The result: The hemp plant's photosynthetic machinery operates at full speed – regardless of the CO₂ levels in the ambient air. More photosynthesis. More energy. More biomass. Potentially more CBD.
The complete program for vital industrial hemp
Step 1 — pH regulation: BODENKRAFT Carbonate of lime
Timing: Before sowing – ideally in the autumn before or early spring.
Hemp requires a pH value between 6.5 and 7.5. Many Austrian agricultural 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 of 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 around 50 percent soil reactivity – and therefore has to be applied in four to six times higher quantities.
Application: 400 to 600 kg per hectare, incorporated once annually.
Step 2 — Soil structure: BODENKRAFT PUR Zeolite
Timing: Before sowing, at the same time as 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) simultaneously – it stores moisture during dry periods and prevents waterlogging during rain. In addition, it improves the cation exchange capacity (the soil's ability to bind nutrients) and retains calcium and nutrients in the root zone.
Application: 300–400 kg per hectare, incorporated.
Step 3 — Activate soil life: AM+PLUS Microorganisms
Timing: At sowing – and then every 3 to 4 weeks.
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 would otherwise remain bound without biological activity. In addition, a living 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-permeable — small enough to penetrate the leaf interior through the stomata). There, the calcium carbonate breaks down into CO₂ for photosynthesis and calcium oxide for cell walls.
GRÜNKRAFT Calcium can be easily combined with all commercially available plant protection products and fertilizers in a single spray application.
First application at the 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. Spray time: Early morning or late afternoon when stomata (leaf pores) are open.
For smaller areas and hobby cultivation, HANFKRAFT is available in a convenient 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 feeder (a plant that requires a lot of nutrients for its rapid growth). In a single season, it extracts significant amounts of calcium, magnesium, potassium, and trace elements from the soil. What it removes must be returned – otherwise, the soil becomes impoverished with each season.
This makes hemp a valuable component 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.
Farmers who cultivate hemp on the same or neighboring areas for several years and simultaneously build up the soil with zeolite, basalt, and microorganisms observe better results each season – because the soil performs more each year.
What farmers observe in practice
Farmers using HANFKRAFT or Grünkraft Calcium on industrial hemp consistently report:
Stronger, more stable plants that do not lodge (fall over) even in bad weather and wind. More uniform development throughout the entire growing season (growth period). More intense leaf color — the dark green indicating 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 of 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 |
| Growing phase | Continue foliar fertilization | GRÜNKRAFT Calcium 3 kg/ha | Every 10–14 days |
| Entire vegetation | Maintain soil life | AM+PLUS | Every 3–4 weeks |
All products for hemp cultivation in our Agriculture Collection.
GRÜNKRAFT Calcium directly — 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 on minerals and degraded soils.
When foliar fertilization and when soil fertilization — the great comparison.
Sources: Upper Austria Chamber of Agriculture, 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
