Choosing the medium: soil, coco or hydroponics?

TL;DR

• Soil: strong buffering, forgiving pH 6.0-7.0.
• Coco: inert, high water holding, pH 5.5-6.5 – behaves like hydro.
• DWC/NFT: fastest growth but sensitive to pump failure and pH drift.
• Roots need oxygen – rhizosphere O₂ is often more limiting than nutrients.

Root zone & oxygen

Cannabis roots have very high O₂ demand. In hydro, keep DO ≥ 6 mg/L via air pumps or venturis. In soil, air porosity (30-40 %) governs root vitality.

Soil, coco or hydroponics: buffer versus control

The substrate primarily determines how quickly mistakes take effect. Soil has the greatest buffering capacity: cation exchange and soil life cushion pH and nutrient fluctuations, but in return, the system reacts sluggishly to corrections. Coco is inert and is run like hydroponics, but retains water like a substrate — it is more forgiving of watering errors than pure hydro systems and requires an adjusted nutrient solution due to the potassium-calcium binding.

Pure hydroponics (DWC, NFT, ebb and flow) delivers the fastest growth rate because oxygen and nutrients are immediately available. The price for this is zero tolerance: a pump failure or an introduction of root rot takes effect within hours. The ideal pH range differs depending on the system — soil 6.0 to 6.8, coco and hydro 5.5 to 6.2 — because nutrient availability depends directly on it.

• Soil: pH 6.0–6.8, watering by weight instead of by schedule
• Coco: buy pre-buffered or treat with calcium-magnesium
• Hydro: nutrient solution 18–20 °C, continuous oxygen input
• Measure drainage (runoff EC/pH) instead of only checking values at the input

Substrate choice and sustainability

Peat-based substrates are under increasing pressure in Switzerland: the Confederation is pursuing a peat phase-out, which is why professional operations are switching to coco, wood fibre, and compost mixes. For product quality, the change is neutral, but not for process management — peat-free mixes dry out faster and require more frequent, smaller waterings.

In Switzerland, the total THC value (THC + THCA × 0.877) alone determines whether a plant is considered industrial hemp or a narcotic. Below 1 %, cultivation is generally permitted; above that, only within the framework of an authorised pilot project under BetmG Art. 8b or with a medical prescription under Art. 8a. Anyone who cultivates themselves bears the burden of proof for the value — the analysis of the harvested batch is decisive, not the variety specification of the seed dealer.

Technical system maintenance and cleaning effort

While used soil must be disposed of or reconditioned after cultivation, hydroponics requires systematic disinfection between cycles. Since organic residues and mineral salts settle in hoses, nozzles and reservoirs, thorough cleaning is absolutely essential to prevent pathogens such as Pythium. This mechanical and chemical cleaning effort is often underestimated compared to the simple disposal of substrates. Those who prefer sterile systems usually use hydrogen peroxide or mild acids to flush the system.

For soil-based cultivation, this intensive sterilisation of the supply lines is completely eliminated, as microbial soil life suppresses pathogenic germs to a certain extent. On the other hand, the question of proper disposal of large quantities of waste substrate arises here, which can pose logistical hurdles in urban areas of Switzerland. Hydroponic systems, on the other hand, generate hardly any solid waste, but require the regular disposal of spent nutrient solution, which must not simply be discharged into the sewage system in an uncontrolled manner.

• Systemic disinfection of all lines with hydrogen peroxide between runs.
• Regular removal of salt encrustations on drippers and nozzles to prevent blockages.
• Logistical effort involved in the disposal or reconditioning of spent soil in urban areas.
• Prevention of biofilms in hydroponic tanks by avoiding organic fertiliser components.

Nutrient management and measuring device calibration

Success in hydroponics stands and falls with the precision of the measuring devices used for pH and electrical conductivity. Since there is no buffer in inert media such as rockwool or expanded clay, incorrectly calibrated probes quickly lead to under- or over-supply of the plants. In contrast to soil cultivation, where visual deficiency symptoms often only appear after several days, hydroponic systems react immediately. An unnoticed shift in pH immediately blocks nutrient uptake, which can lead to irreversible leaf damage.

Regular calibration of the probes using standardised reference liquids is therefore a must for every hydro grower. In addition, these sensitive measuring devices must be stored wet and replaced regularly, as the sensors drift over time. Those who shy away from this technical effort will find a safer alternative in organically fertilised soil. Here, microorganisms take over the processing of nutrients, meaning that minor fluctuations in the irrigation water are balanced out without the constant use of digital measuring tools.

• Weekly calibration of pH and EC probes with calibrated buffer solutions.
• Use of special storage solutions for electrodes to extend their lifespan.
• Immediate reaction of the plants to deviations in the electrical conductivity of the nutrient solution.
• Dispensing with expensive measuring and dosing technology in classic cultivation on organically active soil.

Swiss water quality and regional adjustments

Switzerland has excellent drinking water, which, however, shows significant differences in hardness depending on the region. In lime-rich areas such as the Jura or the Mittelland, tap water is often very hard and contains high amounts of calcium and magnesium. For soil cultivation, this is usually advantageous, as these minerals serve as a natural buffer and stabilise the pH value. In hydroponics, on the other hand, very hard water quickly leads to uncontrolled nutrient precipitation and blocked pipes without prior treatment using a reverse osmosis system.

Conversely, alpine regions often have very soft, mineral-poor water, which must be specifically enriched with calcium and magnesium preparations in hydroponic systems to prevent deficiencies. When cultivating within the framework of Swiss pilot trials in accordance with BetmG Art. 8b or when producing legal cannabis with less than one percent THC, cantonal water protection regulations must also be observed. Discharging nutrient-rich wastewater from hydroponic systems into the sewerage system is strictly regulated and often requires professional disposal.

• Consideration of the regional hardness level of Swiss tap water in fertiliser formulation.
• Necessity of reverse osmosis systems in regions with highly calcareous drinking water.
• Compliance with cantonal water protection ordinances when disposing of spent nutrient solution.
• Targeted supplementation of calcium and magnesium when using soft alpine water.

Risk management in the event of power outages and system failures

The greatest operational risk in hydroponics is the dependence on a continuous power and water supply. If a pump fails in an aeroponic or deep water culture system, the exposed roots dry out within a very short time due to a lack of moisture and oxygen. Just a few hours without circulation can lead to the total loss of the entire crop. In soil cultivation, on the other hand, the substrate stores moisture for days, meaning that technical defects or power interruptions are usually survived without serious consequences.

Professional risk management is therefore essential for hydroponic systems and requires additional investment in safety infrastructure. This includes uninterruptible power supplies for the most important pumps as well as automatic alarm systems that report deviations in water temperature or fill level directly to a mobile phone. Those wishing to minimize this risk choose hybrid systems such as coco coir or classic soil, which offer a natural safety buffer and give the grower valuable response time in the event of technical malfunctions.

• Installation of backup generators or battery systems to bridge grid failures.
• Use of temperature sensors to monitor the nutrient solution in order to prevent root rot.
• Use of mechanical float valves as physical overflow protection in the water tank.
• Use of coco substrate as a safety buffer between pure hydroponics and classic soil.

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