Sonnenerde Organic Cannabis Soil: The soil that thinks.

Sonnenerde’s organic cannabis soil is not your typical hardware store substrate. It is the result of over 30 years of compost research, an ancient soil concept from the Amazon, and a company philosophy that closely connects climate protection with plant cultivation. What exactly is happening inside this soil — and why does cannabis benefit so strongly from it?

2. Terra Preta: The foundation of Bio Hanferde

To understand how Bio Hanferde works, you first need to understand the principle of Terra Preta. This knowledge was essential to create an extremely fertile soil that delivers top yields without any added fertilizers.

Terra Preta (Portuguese for “black earth”) was developed thousands of years ago by indigenous peoples in the Amazon region. The foundation of this deep black, highly fertile soil is biochar, combined with organic waste from settlements at the time and Amazonian sediments rich in minerals and trace elements. While conventional soils tend to lose nutrients quickly through rainfall, the biochar in Terra Preta acts like a massive microscopic sponge, retaining these nutrients and releasing them when needed.

Its high fertility is the result of this unique composition and a highly diverse microbial ecosystem. The characteristic dark color of Terra Preta comes from its high carbon content in the form of stable humus. What the indigenous people of the Amazon developed intuitively has been replicated by Sonnenerde in an industrial, reproducible process and optimized for modern plant cultivation.

What makes biochar so special?

Biochar is produced through pyrolysis—organic material is carbonized at around 600 °C in the absence of oxygen. The result is a highly porous carbon structure with an enormous internal surface area: one gram of biochar can have a surface area of several hundred square meters.

These pores store water and nutrients while providing an ideal habitat for microorganisms. With 1,000 tons of biochar, around 2,500 tons of CO₂ can be bound in the soil for centuries. Climate protection and plant growth therefore go hand in hand.

3. The ingredients: What’s inside Bio Hanferde?

Bio Hanferde is produced using the most gentle, environmentally friendly, and natural processes possible, with a strong focus on sustainability, regional sourcing, and quality. Through hot composting, aerobic, humus-building soil organisms and fungi are promoted, ensuring optimal nutrient availability for plants. Each ingredient plays a clearly defined role within the overall system:

Organic compost:

The origin of the microbiome, containing a diverse soil life of bacteria, fungi, protozoa, and nematodes. Hot composting specifically activates aerobic organisms that release nutrients according to plant demand.

(Charged) biochar:

The Terra Preta element. “Charged” means the biochar has already been inoculated with nutrients and microorganisms before being mixed in. Raw biochar would initially bind nutrients from the soil. It acts as a water reservoir, mineral storage, microbial habitat, and CO₂ sink.

Acidic compost:

Provides stability. This is another area where Sonnenerde has done pioneering research. The permanently stable acidic compost is essential for adjusting the pH of compost-based soils.

Horn shavings:

A slow-release organic nitrogen source. They are gradually broken down by soil fungi, making nitrogen available to plants over time. A white fungal network on the surface is not mold, but a sign of active microbial life. The release rate adapts to plant demand.

Soft rock phosphate:

A natural phosphorus source that is gradually made available by acid-forming microorganisms in the substrate. Phosphorus is essential for flowering and energy transfer within the plant.

Expanded clay granules:

Fired clay used for structure and drainage. It prevents compaction, stores moisture through capillary action, and ensures a permanently loose and aerated substrate—crucial for oxygen supply to aerobic microbes.

Perlite (Agroperl):

A purely thermally expanded mineral. Compared to wood fiber, it maintains structural stability much longer and makes the soil significantly lighter and more aerated.

4. What happens inside Bio Hanferde during the grow?

The core of Bio Hanferde is not a single ingredient—it’s the interaction of all components within a living system. Soil-dwelling fungi, bacteria, and other microorganisms supply the plant with nutrients from the organic matter present in the soil and even from the air. For example, fungi gradually break down the nitrogen stored in horn shavings, while certain bacteria (e.g. Azotobacter) bind nitrogen from the surrounding air.

Nutrient supply often occurs through symbiosis: microbial life receives sugars produced by the plant through photosynthesis in return for making nutrients available.

This exchange between plant roots and microorganisms is the key principle. The cannabis plant actively controls which microbes are promoted in its immediate environment through the release of root exudates—thereby directly influencing which nutrients are made available and in what quantities. The substrate responds to the plant’s actual needs, not to a fixed feeding schedule.

Charged biochar plays a central role as a biochemical network. It enables the system to provide large amounts of nitrogen during the vegetative phase and to transition toward increased potassium and phosphorus demand during flowering—without additional fertilization. Its porous structure offers microorganisms a stable, protected habitat that can even withstand short periods of drought. Nutrients are retained within the pores instead of being washed out and are released again when needed through microbial activity.

Vegetative vs. flowering phase: how the system adapts

During the vegetative phase, cannabis has a high demand for nitrogen. The roots signal this need via exudates, which increases the activity of nitrogen-fixing bacteria and fungi that decompose horn shavings.

In the flowering phase, demand shifts toward phosphorus and potassium. Minerals stored in soft rock phosphate are gradually made available by acid-producing bacteria. In this way, Bio Hanferde supports optimal plant growth during the vegetative stage and enables a rich expression of active compounds—cannabinoids, terpenes, and other secondary metabolites—during flowering.

5. USPs of Bio Hanferde

What sets Bio Hanferde from Sonnenerde apart from other substrates on the market can be summarized in six key points:

Truly “ready to grow”:

From a pot size of 15 liters combined with an organic mulch layer, only water is needed throughout the entire plant lifecycle. No feeding schedule, no pH obsession, no EC meter. The soil fully regulates nutrient supply on its own.

Strong buffering capacity:

Its buffering effect compensates for fluctuations in pH, climate conditions, and minor cultivation mistakes. This ensures consistently high quality and provides a significant safety margin—especially for less experienced growers.

Peat-free & regional:

Bio Hanferde is produced mainly from regional raw materials and completely avoids peat and coco coir. Peat extraction destroys peatlands—one of the planet’s most important CO₂ sinks—while coco coir requires long-distance transport. Both have been deliberately avoided since the company’s founding.

CO₂-negative through biochar:

Thanks to the combination of biochar, microorganisms, and organic biomass, Bio Hanferde actively binds CO₂ during production. Each bag therefore acts as a certified carbon sink.

Reusable & regenerable:

Reusing the soil is not only possible but encouraged and aligns with Sonnenerde’s philosophy. After the first cycle, most macro- and micronutrients—except nitrogen—are still available for multiple runs. In most cases, refreshing with 5 g/L of horn shavings is sufficient. Alternatively, Sonnenerde’s soil activator can be mixed into the used substrate at 10% by volume, with minimal risk of over-fertilization. With proper care, the substrate becomes biologically richer with each harvest.

Research-based & scientifically validated:

Through intensive research in collaboration with the University of Graz, a microbial composition was developed that closely matches original Terra Preta. No other ready-to-use grow soil in the German-speaking market can point to a comparable scientific foundation.

7. Limitations & honest assessment

No substrate can perform miracles—not even Bio Hanferde from Sonnenerde. For example, Sonnenerde recommends starting seedlings in a separate propagation soil and/or transplanting well-rooted cuttings or seedlings into Bio Hanferde to avoid stress from excess nitrogen at the beginning. If you want to sow seeds directly, you can place a small amount of seed-starting soil in the center of the pot.

The smaller the pot, the more challenging living soil becomes in general—and this also applies to Bio Hanferde. On one hand, moisture levels fluctuate more strongly; on the other, the nutrient reservoir is more limited. Combined with a potentially less stable soil biology, this can more easily lead to nutrient deficiencies. That said, there are already successful real-world examples using very small pots—though the level of difficulty for the grower increases accordingly.

Finally, Bio Hanferde is priced above conventional grow substrates. However, if viewed as a long-term investment—reused, refreshed, and continuously recycled—the cost quickly balances out. When factoring in the elimination of liquid fertilizers, pH adjusters, and other additives, the overall value becomes much more apparent.