Key parameters for healthy plants
Key parameters to monitor:
- pH (potential hydrogen or acidity)
- EC (electrical conductivity)
- Root-zone temperature
In this article, we will examine each of these parameters in detail—how they affect plants, the consequences of values that are too high or too low, and how to adjust them safely in your growing environment.
⚠️ Remember: it is always easier to prevent deficiencies than to treat them afterwards.
Key parameters for plant health—pH, EC, and temperature ?
Author: Kasha Dubaniewicz
Kasha is passionate about high-impact stories and believes in creating positive change that leads to a better, happier world for everyone.
Why are nutrient deficiencies a problem?
Nutrient deficiencies in plants can create a number of challenges. They are often difficult to recognise, and treating them is not always effective.
Visually, many deficiencies look the same—yellowing leaves, brown edges, or stunted growth. Plants often suffer from several different deficiencies at the same time, making treatment even more complicated.
? It is easier to manage the key parameters of plant health—pH, EC, and temperature—than to treat problems that have already developed.
Article contents
- What is pH?
- The role of pH in nutrient uptake
- Effects of incorrect pH
- How to lower pH
- How to raise pH
- What is EC?
- The role of EC in nutrient uptake
- Effects of incorrect EC
- How to lower EC
- How to raise EC
- Why is temperature important for growth?
- The role of root-zone temperature
- Effects of incorrect temperature
- How to lower root-zone temperature
- How to raise root-zone temperature
What is pH?
pH (potential hydrogen) is a scale that measures the acidity or alkalinity of a solution—in this case, the nutrient solution or soil.
When you measure pH, the result is based on the number of hydrogen ions (H+).
- More H+ means a more acidic environment (pH 0–7).
- Less H+ relative to hydroxyl groups (OH-) means an alkaline environment (pH 7–14).
- A value of pH 7 is considered neutral.
The role of pH in nutrient uptake
All plants need a balanced range of nutrients to grow healthily. Your pH level determines whether those nutrients are available for uptake.
Nutrients must be water-soluble and carry an electrical charge, either positive or negative. Each element has its own "preferred" pH range in which it is available to plants.
Outside that range, a phenomenon known as "nutrient lockout" occurs: plants cannot absorb their food even when it is present. This can also happen when fertilisers are overapplied.
?️ You can think of pH as a "key" that unlocks nutrients and makes them available to plants.
Recommended pH values
- Hydroponics: 5.8 – 6.5
- Soil: 6.5 – 7.0
⚠️ Some crops have specific requirements—always check the preferred range of the plants you are growing.
Effects of incorrect pH
Because pH determines nutrient uptake, the wrong range will inevitably cause symptoms:
When pH is too low (acidic conditions):
- Risk of iron and manganese toxicity.
- Deficiencies of magnesium, calcium, and phosphorus.
- Visible symptoms: yellow spots, necrosis, dried tips, and stunted growth.
When pH is too high (alkaline conditions):
- Many elements become insoluble and "locked out".
- Copper and zinc deficiencies are common.
- Visible symptoms: interveinal chlorosis, brown spots, necrosis, and curled leaves.
How to lower pH
[Phosphoric acid treatment]
As the tables above show, most plants prefer a slightly acidic growing environment. If you measure the pH and notice that the value is rising, there are several ways to correct it, depending on your growing method.
In hydroponics:
- Phosphoric acid or ready-made pH Down products are most commonly used to lower the pH of a nutrient solution.
- Always dilute the acid before adding it to the solution! The recommended ratio is 1:10 (1 part acid to 10 parts distilled or reverse-osmosis water).
- Add the diluted acid gradually, measuring the pH to prevent it from falling too sharply.
- Common practice is to use:
- nitric acid during the growth period;
- phosphoric acid during flowering.
- Always wear gloves and safety goggles when working with acids.
In soil:
- The most common option is to add sulphur, which is broken down slowly by bacteria and gradually lowers the pH.
- Organic materials such as compost or manure also work, but their effect is slower.
- For faster results, you can use aluminium sulphate, which works immediately but poses a risk of toxicity if overapplied.
- Other popular amendments include coffee grounds and peat, but always consult a specialist and establish the type of soil, such as sandy or clay soil.
How to raise pH
[Powdered lime spread over soil or potassium silicate in ready-made pH Up solutions]
If you measure a pH that is too low, meaning the environment is too acidic, you need to raise it by making the soil or solution more alkaline.
In hydroponics:
- Bicarbonates are most commonly used, for example potassium silicate or ready-made pH Up solutions.
- Always dilute at a ratio of 1:10 (1 part pH Up to 10 parts distilled or RO water).
- Add it gradually, measuring the value to avoid exceeding the target range.
- If you have access to hard water, it can be used as a natural buffer that raises pH slightly, but only for small adjustments.
- Always wear safety goggles and gloves while working.
In soil:
- The process is known as liming—the most commonly used material is powdered limestone.
- Finely ground limestone works fastest.
- Granulated lime or lime pellets break down more slowly.
- Other options:
- calcitic lime (pure calcium),
- dolomitic lime (which also adds magnesium).
- Wood ash also raises pH gradually and is an economical solution, though it is less effective than lime.
⚠️ Important: lime products and ash can irritate the skin and respiratory tract. Always use a mask and gloves.
What is EC?
[Bluelab Pulse Meter measures EC in soil]
EC (electrical conductivity) is a measure of the total quantity of nutrients available to plants.
When nutrients dissolve in water, they separate into ions that carry an electrical charge. This allows the solution to conduct electricity. Pure water does not conduct electricity because it contains no ions. The more ions there are in the solution, the higher its electrical conductivity.
How is EC measured?
- It is measured in mS/cm (millisiemens per centimetre).
- Unlike pH, there is no universal scale—at least four different scales are used:
- EC (Electrical Conductivity): 1 mS/cm = 1 EC
- PPM 700: EC × 700
- TDS / DS / MS (PPM 500): EC × 500
- CF (Conductivity Factor): EC × 10
? It is important to know which scale your instrument and fertiliser supplier use.
⚠️ EC indicates the total quantity of nutrients, but not their specific composition.
? For a detailed introduction, see the article: "What is electrical conductivity and how is it measured?"
Recommended product: Bluelab Pulse Multimedia EC/MC Meter
The role of EC in nutrient uptake ?
[Healthy green leafy crops in a large greenhouse]
At the most basic level, nutrients must be present for plants to absorb them. Measuring EC gives you an indication of the total quantity of ions—or nutrients—currently in your system.
You may be tempted to feed plants as much as possible so that they always have access to food, but this can have catastrophic consequences. Every crop has a preferred EC range in which it develops optimally.
? Different crops require different nutrient-solution strengths depending on their growth stage. It is good practice to research the specific crop or consult a specialist to ensure that you maintain the correct range throughout its growth.
EC affects not only nutrient uptake, but also the ability of plants to absorb water. If conductivity is too high, plants may be unable to take up enough water.
- In hydroponics: measure the EC of the nutrient solution when mixing it and again after plants have taken it up.
- In soil: measuring fertiliser strength is more difficult because fertilisers need time to break down. However, it is possible to measure EC directly in the root zone with a soil EC meter.
? EC values fluctuate, so it is important to measure them daily, especially on warm days when plants may take up only water.
Hydroponic growers should make a habit of emptying the reservoir completely and replacing the nutrient solution every 7–10 days. This prevents imbalances in nutrient composition that could lead to deficiencies or toxicities.
Effects of incorrect EC ⚠️
As the tables show, each crop has its own preferred EC range. If plants are exposed to unsuitable values, they begin to show symptoms of poor health.
When EC is too low:
- Leaf discolouration (yellow or brown tones)
- Holes or brown necrotic spots
- Stunted root and foliage growth
- Reduced yield
- Deformed or twisted leaves
When EC is too high:
- Toxicities—interveinal chlorosis, thickened or necrotic roots, brown spots, and changes in leaf size.
- Sodium/salt burn—burnt tips and edges, and twisted or curled leaves.
- Water deficiency—wilting leaves and stems, loss of lustre, and stunted growth.
? Instead of treating symptoms, measure EC regularly, regardless of your growing method.
Recommended instruments for measuring EC:
- Bluelab Conductivity Pen
- Bluelab Pulse Multimedia EC/MC Meter
- Bluelab Truncheon Nutrient Meter
- Bluelab Combo Meter
How to lower EC
[Water]
- In hydroponics: add pH-balanced water to dilute the salts. If the values are very high, you may need to flush the system completely and replace the solution with a weaker one.
- In soil: water thoroughly with pH-balanced water until the soil is saturated and drains. Measure the EC of the soil runoff and repeat if necessary.
How to raise EC
[Measuring EC with a Bluelab Combo Meter]
- In hydroponics and soil: simply add more nutrient solution or fertiliser.
- Always measure EC after adding fertiliser and stirring the solution to avoid exceeding the target range.
⚠️ This is different from treating a specific deficiency—for those cases, see the guide to nutrient deficiencies.
Recommended product: Bluelab Combo Meter
Why is temperature important for plant growth? ?️
[A thermometer measures the temperature in your garden]
pH and EC are critical parameters for plant health, but temperature also plays a crucial role in optimal growth. It is also the parameter most often overlooked.
Temperature can refer both to the air around the plants and to the temperature of the nutrient solution or irrigation water, which directly affects the root zone.
The roots are where two vital processes take place:
- water uptake;
- nutrient uptake.
? To function efficiently, roots must be kept within an optimal temperature range.
The role of root-zone temperature in nutrient uptake
[Young seedlings under LED lighting]
Root-zone temperature determines the rate at which plants absorb nutrients. If it is left uncontrolled, it can cause serious yield losses.
- Optimal range: 18–22 °C (65–72 °F).
- If the water is too warm → less dissolved oxygen → risk of oxygen deprivation.
- If the water is too cold → shock to the roots, slower metabolic processes, and stunted growth.
As with pH and EC, every crop has its own preferred root-temperature range.
Effects of incorrect root-zone temperature
- In soil: temperature fluctuations are smaller because the soil acts as a buffer.
- In hydroponics: roots are more vulnerable to sudden changes.
❌ If the temperature remains too high or too low for an extended period, plants can enter a "dormant" state—growth and yield decline dramatically.
When the temperature is too high:
- Accelerated metabolic reactions → risk of toxicities (leaf discolouration and thickened/necrotic roots).
- Increased risk of pathogens and diseases.
- Reduced dissolved oxygen content → problems with plant respiration.
When the temperature is too low:
- Slower metabolism → nutrient deficiencies.
- Symptoms: interveinal chlorosis, stunted growth, brown edges or spots, and leaf necrosis.
- As with high temperatures, there is a risk of disease and infection.
How to lower root-zone temperature ?️
[Growers inspect plants in a shaded environment]
In hydroponics:
- Use chillers with a built-in thermostat.
- A popular option is to place stainless-steel cooling coils in the reservoir.
- Insulate the reservoir to maintain more stable temperatures.
In soil:
- Plant cover crops to provide shade and reduce evaporation.
- Use shade covers or netting in summer.
- Apply mulch or synthetic ground covers for insulation.
How to raise root-zone temperature ?
[Healthy seedlings growing on mulch]
In hydroponics:
- Use an additional reservoir in which the water can warm up before entering the system.
- In cold climates, use heated reservoirs or mechanical heaters with a heat exchanger, as the solution is corrosive.
- Insulate the reservoir and raise it off concrete surfaces.
In soil:
- Install heating cables or use thermostatically controlled heating mats.
- Mulching in winter prevents cooling and retains heat.
- Use additional covers such as plastic, organic, or synthetic insulation.
? Maintaining the correct pH, EC, and temperature values is the foundation of successful plant cultivation. They determine whether plants can absorb the nutrients and water needed for healthy, productive growth.
? Make a habit of measuring these parameters regularly and adjusting them when necessary. This will spare you many problems and ensure better results.
