The optimal pH value for plants: everything you need to know

Why is pH Level Important for Plants?

The pH level of irrigation water and substrate is a crucial factor for plant growth and health. It directly affects nutrient absorption and can determine whether you achieve a bountiful harvest or experience nutrient deficiencies.

Plants can only absorb nutrients optimally when the pH level is within the ideal range. If it is too high or too low, essential macro- and micronutrients either become unavailable or are absorbed in harmful concentrations. This leads to growth problems, deficiencies, or even toxic reactions.

The Optimal pH Level for Different Substrates:

• Soil: 6.0 – 7.0
• Hydroponics: 5.5 – 6.5
• Coco Substrate: 5.8 – 6.2

Understanding pH: What Does It Mean?

The pH level indicates whether a solution is acidic or alkaline. It is measured on a scale from 0 to 14:

• pH 0–6.9: acidic
• pH 7: neutral (e.g., pure water)
• pH 7.1–14: alkaline/basic

Depending on the pH level, nutrients are absorbed more or less effectively. An improperly adjusted pH level can block essential nutrients or make them excessively available, leading to nutrient deficiencies or toxic reactions.

How to Accurately Measure pH Levels

The pH level can be determined using various methods:

1. pH Meter: The most precise method, especially for regular measurements.
2. pH Test Strips: Affordable but less accurate.
3. Drop Tests: A good alternative for quick checks.

Important Measurement Points:

• Measure irrigation water before watering.
• Test the runoff water after watering to assess the substrate's pH level.

Tip: The pH level of the substrate can be determined through a soil analysis. This provides more accurate information about the condition of the medium.

What Happens if the pH Level is Incorrect?

A pH level that is too low or too high can have serious consequences for plants:

• Too acidic (pH < 5.5):

  • Blocks calcium, magnesium, and phosphorus
  • Leads to root stress
  • Increases the risk of toxic metal accumulation

• Too alkaline (pH > 7.5):

  • Reduces iron, zinc, and manganese absorption
  • Leads to chlorosis (yellow leaves due to iron deficiency)
  • Disrupts soil microbiology

Long-term deviations from the ideal pH level can result in reduced yields and poor plant quality. Therefore, it is crucial to regularly check and adjust the pH level if necessary.

How to Adjust the pH Level

If your pH level is not within the optimal range, there are several ways to correct it:

Lowering the pH Level (Acidic Adjustment)

• Adding citric acid or vinegar (for short-term adjustments)
• Sulfuric acid or phosphoric acid (for long-term reduction)
• Organic materials such as peat or compost

Increasing the pH Level (Alkaline Adjustment)

• Dolomitic lime or garden lime
• Wood ash or potassium bicarbonate
• Natural additives such as oyster shell flour

Important: Always make adjustments gradually and regularly measure the pH level to avoid overcorrections.

Organic Cultivation: Is pH Monitoring Necessary?

In organic cultivation, microorganisms play a crucial role in nutrient availability. While soil microbiology can regulate itself to some extent, checking the pH level can help prevent deficiencies.

Organic Methods for pH Regulation:

• Compost tea or worm castings: Stabilizes the pH level long-term.
• Zeolite or clay minerals: Bind acids and act as a natural pH buffer.
• Rainwater instead of tap water: Often has a better pH level for plants.

Nutrient Uptake and pH Level: What You Should Know

An optimally adjusted pH level is essential for nutrient absorption:

Depending on the growth phase, slightly varying the pH level within the recommended range can be beneficial to enhance nutrient absorption.

Products for Measuring pH Levels at Cannadusa

Aqua Master Handheld meter H600 Pro Soil/Substrate - €299.00

Aqua Master Tools Combo Pen P160 Pro pH EC TDS PPM Temperature - €105.00

Bluelab Pulse Multimedia Meter - €349.00