| Definition | Measures the acidity or alkalinity of a solution, ranging from 0 (highly acidic) to 14 (highly alkaline), with 7 being neutral. |
| Role | Determines the availability of nutrients to your plants. |
| Importance | Out-of-range pH levels can block nutrient absorption, causing deficiencies even when nutrients are present. |
| Definition | Indicates the concentration of dissolved salts (nutrients) in the solution, measured in milli Siemens per centimetre (mS/cm) or parts per million (PPM). |
| Role | Reflects the nutrient strength and concentration in the solution. |
| Importance | Ensures balanced feeding by avoiding overfeeding (nutrient burn) or underfeeding (nutrient deficiencies). |
The ability of plants to absorb nutrients depends heavily on maintaining pH levels within specific ranges. Cannabis plants have different optimal pH levels depending on the growing medium:
| Soil | 6.0–6.0 |
| Coco Coir | 5.7–6.2 |
| Hydroponics | 5.5–6.0 |
| EC level | Meaning | Risk |
| High EC | Indicates a nutrient-rich solution. | Nutrient burn or salt buildup, potentially harming plants. |
| Low EC | Indicates insufficient nutrients. | Slow growth or nutrient deficiencies, leading to poor plant health. |
The needs of your cannabis plants change as they progress through the various growth phases. Adjusting pH and EC at each stage ensures optimal nutrient uptake.
| Soil | Coco Coir | Hydroponics | ||||
| Phase | pH | EC | pH | EC | pH | EC |
| Germination | 5.7–6.0 | 0.3–0.6 | 5.5-6.0 | 0.3–0.6 | 5.5–6.0 | 0.3–0.6 |
| Minimal nutrients; stable pH & light feed. | ||||||
| Seedling | 6.0–6.5 | 0.6–0.8 | 5.7–6.2 | 0.8–1.0 | 5.5–6.0 | 0.9–1.2 |
| Sensitive to strong feeds; gentle balance. | ||||||
| Early Vegetation | 6.0–6.5 | 0.8–1.0 | 5.7–6.2 | 1.0–1.2 | 5.5–6.0 | 1.2–1.4 |
| Increased nitrogen uptake; leaf and root growth. | ||||||
| Main Vegetation | 6.0–6.5 | 1.0–1.4 | 5.7–6.2 | 1.2–1.6 | 5.5–6.0 | 1.4–1.8 |
| Nitrogen-dominant feeding for vigourous growth. | ||||||
| Late Vegetation | 6.0–6.5 | 1.4–1.6 | 5.7–6.2 | 1.6–1.8 | 5.5–6.0 | 1.8–2.0 |
| Balanced feeding; plant prepares for flowering. | ||||||
| Pre-Flowering | 6.0–6.5 | 1.6–1.8 | 5.7–6.2 | 1.8–2.0 | 5.5–6.0 | 2.0–2.2 |
| Higher phosphorus & potassium requirements. | ||||||
| Blooming | 6.0–6.5 | 1.8–2.2 | 5.7–6.2 | 2.0–2.4 | 5.5–6.0 | 2.2–2.6 |
| Peak phosphorus and potassium demand. | ||||||
| Ripening | 6.0–6.5 | 0.8–1.0 | 5.7–6.2 | 1.0–1.2 | 5.5–6.0 | 1.2–1.4 |
| Minimal nutrients; preparation for final flush. | ||||||
| Flushing | 6.0–6.5 | 0.0–0.4 | 5.7–6.2 | 0.0–0.4 | 5.5–6.0 | 0.0–0.4 |
| Flush salts and enhance flavour. | ||||||
To lower the pH, just a single drop of solution is enough. However, to raise it, significantly more is required!
Consider using drip trays or floor mats in high-watering zones to catch excess water and prevent floor damage.
| pH metre | Essential for precise pH readings. |
| EC metre | Measures nutrient strength effectively. |
| pH adjusters | Products like pH up/down solutions to balance pH. |
| Storage solution(s) | Keeps metre probes functional for accurate readings. |
| 1. | pH controls nutrient availability; EC ensures appropriate feeding strength. Maintaining the correct pH and EC ensures your plants get the right nutrients at the right time. |
| 2. | Regular monitoring prevents nutrient imbalances. Consistent testing helps avoid deficiencies or toxicities. |
| 3. | Tailoring pH and EC to each growth phase maximises health and yield. Each growth phase has specific needs—adjust pH and EC accordingly for the best results. |
| ppm (parts per million) | Measures the concentration of dissolved salts in the nutrient solution. |
| EC (Electrical Conductivity) | Indicates the ability of the solution to conduct electricity, measured in milli Siemens per centimetre (mS/cm) or micro Siemens (µS/cm). |
| EC (mS/cm) |
500 scale (Hanna) –ppm |
640 scale (Eutech) –ppm |
700 scale (Truncheon) –ppm |
| 0.1 | 50 | 64 | 70 |
| 0.2 | 100 | 128 | 140 |
| 0.4 | 200 | 256 | 280 |
| 0.6 | 300 | 384 | 420 |
| 0.8 | 400 | 512 | 560 |
| 1.0 | 500 | 640 | 700 |
| 1.2 | 600 | 768 | 840 |
| 1.4 | 700 | 896 | 980 |
| 1.6 | 800 | 1024 | 1120 |
| 1.8 | 900 | 1152 | 1260 |
| 2.0 | 1000 | 1280 | 1400 |
| 2.4 | 1200 | 1536 | 1680 |
| 3.0 | 1500 | 1920 | 2100 |
| 500 scale (Hanna Instruments) | Commonly used in North America. |
| Conversion factor: 1 mS/cm = 500 ppm. | |
| Best suited for traditional hydroponic setups. | |
| 640 scale (Eutech Instruments) | Frequently used in Australia and parts of Europe. |
| Conversion factor: 1 mS/cm = 640 ppm. | |
| Typically aligns with soil-based or less saline solutions. | |
| 700 scale (Truncheon) | Widely used in New Zealand and by advanced growers. |
| Conversion factor: 1 mS/cm = 700 ppm. | |
| Preferred for high-precision commercial setups. |
| Sensor rinsing | pH | Use fresh water |
| EC | Use fresh wate | |
| Immersion in solution | pH | Calibration solutions (pH 4.0 and 7.0) |
| EC | EC calibration solution | |
| Instrument adjustment | pH | Follow the manufacturer’s instructions |
| EC | Adjust to the calibration solution’s value | |
| Storage | pH | In storage solution |
| EC | Clean and store dry |
Never store pH or EC sensors in deionised or RO water, as this can damage the sensing membrane. Always consult the manufacturer's instructions!
Never mix pH up and pH down solutions directly in their concentrated forms. The chemical reaction can generate intense heat & dangerous fumes, posing a severe safety risk.
Always handle these chemicals with care, using separate, colour-coded pipettes or tools for each solution to prevent cross-contamination.
Adjust pH by adding small amounts of each solution to water separately, testing regularly to achieve the desired range.
pH affects nutrient availability. Incorrect pH levels cause nutrient lockout, leading to deficiencies even when nutrients are present.
The optimal pH range for soil is 6.0–6.5.
Use a calibrated digital pH metre and test nutrient solution or runoff water.
EC measures nutrient concentration, preventing overfeeding or underfeeding.
High EC can cause nutrient burn. Flush the medium with pH-balanced water to reduce EC.
Tap water may require pH adjustment and dechlorination. Test it before use.
Calibrate regularly, ideally every 1–2 weeks or before critical measurements.
Lockout occurs when improper pH blocks nutrient uptake. Maintain correct pH levels to avoid it.
Runoff pH changes indicate substrate imbalances or salt buildup. Adjust with flushing or corrective feeding.
ppm measures nutrient concentration using a conversion from EC. EC is more precise and universally standardised.
Adjust pH gradually with small doses of pH up/down solutions, rechecking frequently.
Look for symptoms like yellowing leaves (deficiencies) or burnt tips (toxicity).
Yes, organic nutrients may naturally buffer pH, requiring less adjustment.
Drift occurs as plants absorb nutrients and release ions, altering solution pH. Monitor and adjust regularly.
Essential tools include a pH metre, EC metre, pH adjusters, and calibration solutions.
Reuse is possible after testing pH and EC. However, beware of accumulated salts or contaminants.
1 mS/cm equals 500 ppm on the Hanna Scale, 640 ppm on the Eutech Scale, or 700 ppm on the Truncheon Scale.
Use pH-balanced water at low EC (0.0–0.5 mS/cm), applying 2–3× the pot volume.
Poor-quality water with high TDS (Total Dissolved Solids) can skew pH and EC, leading to inaccurate nutrient delivery. Use RO water or filtered water for precision.