Do you have everything under control, but your plants still show signs of deficiency? The leaves are turning yellow, growth is slowing down, and the fruits are not ripening… It may not be a lack of fertiliser, but quite the opposite: a nutrient lockout.
Nutrient lockout occurs when nutrients are present in the substrate, but the plant cannot absorb them. They are there, but inaccessible. And if we don’t act in time, the symptoms can worsen and compromise the entire crop.
This problem is especially common in soil crops, where factors such as pH, irrigation quality and nutrient interactions play a key role. If you use fertilisers (whether mineral or organic) and your plants stop responding as they should, don’t ignore it: early detection of the lockout is crucial to start recovery from nutrient lockout and prevent further damage.
To prevent (or recover your plants) from a nutrient blockage, just read this article where we explain in depth:
What is a nutrient blockage?
What are the main causes?
Keys to preventing it and,
if it’s too late, how to correct a nutrient blockage.
Stay with us to find out.
What is nutrient blockage and how can you recognise it?
In simple terms, nutrient lockout is a phenomenon in which the roots of the plant are unable to absorb certain nutrients, even though they are available in the substrate. As a result, the plants look sick, wilted or stunted.
The problem is obvious, but it is not easy to identify.
A nutrient blockage can lead to symptoms of deficiencies that are easily confused with a lack of nutrition, so we increase the dose, aggravating the problem.
What is happening is not a lack of nutrients, it is a failure in how they are absorbed (or not).
How can you recognise it?
The most common symptoms of nutrient blockage are the same as those of a deficiency because, after all, that is what is happening. Remember that a blockage leads to poor nutrient absorption and, therefore, to a deficiency in the plant. So, we look for:
• Yellow leaves or leaves with brown spots.
• Burnt or curled edges.
• Slow or stunted growth.
• Small or misshapen fruits.
• Apparent deficiencies despite correct fertilisation.
The key here is to know that you are fertilising correctly and then to understand the causes of nutrient blockages so that you can avoid them.
In addition, to help you identify which nutrient may be blocked based on the symptoms, many growers use a nutrient blockage chart.
These charts show the pH ranges in which each nutrient is properly absorbed, allowing you to:
✅ Adjust the pH of your soil or nutrient solution to prevent blockages.
✅ Detect whether a deficiency symptom is really due to a lack of nutrients… or to an incorrect pH.
✅ Optimise the yield and health of your crops.
Let’s look at the main causes that prevent our plants from absorbing nutrients normally:
Key factors that cause nutrient blockages (and how to keep them under control)
Now that we know what a nutrient lockout is and have an idea of its causes and symptoms, let’s take an in-depth look at the three main culprits — and what you can do to prevent them.
Substrate pH: the invisible lockout
Soil pH is not tangible, nor is it something we can see with the naked eye, yet it is one of the most critical factors for nutrient absorption.
If the pH is outside the ideal range, many essential elements are simply unavailable to the plant, even if they are present. It’s that simple (and that frustrating).
Each nutrient needs a specific pH range to be absorbed. If the pH falls outside these margins, whether too acidic or too alkaline, some elements become ‘locked’.
What is the optimal pH range?
It really depends on the plant, the type of substrate and other factors. But we can give you some safe general guidelines, so you don’t go wrong:
• For soil, universal substrates and potting mixes: 6.0 -6.5
• Cultures in coco: 5.8 – 6.2
• Hydroponic cultures: require a more precise pH, between 5.5 and 6.2
A pH below 5.5 can block calcium and magnesium. Above 7.0, phosphorus and iron are the first to be knocked out of action.
To simplify things: if you keep your pH between 5.5 and 6.5, that should be sufficient.
Key tips:
• Measure the pH regularly with a reliable meter. You can use test strips, but they are more prone to error.
• Adjust with pH correctors if necessary.
• Use pH-balanced fertilisers, such as those from Atami, formulated to maintain a stable environment and reduce the risk of blockages due to imbalances.
Remember that a good pH is the gateway to effective nutrition.
Nutrient interactions: when one interferes with another
It’s not just pH that can cause blockages; some nutrients can also block each other.
Certain interactions can cause antagonisms that block the absorption of other elements. This is another of the most common causes of nutrient blockages.
Classic examples:
• Excess potassium (K) → blocks the absorption of magnesium (Mg) and calcium (Ca).
• Excess phosphorus (P) → can interfere with zinc (Zn) or iron (Fe).
• High doses of nitrogen (N) → can unbalance the rest of the macro and micronutrients.
Pro tip:
Keeping a growing diary with notes on watering, fertilisation and observations helps you detect patterns. In addition, following the recommended growing charts from manufacturers such as Atami allows you to maintain balanced nutrition and avoid mistakes.
In summary: an excess of nutrients can block absorption by altering the balance of the growing medium.
Root diseases:
Not all blockages are chemical. Diseased or damaged roots are also unable to absorb nutrients properly, which can lead to deficiencies, even if your substrate is well nourished.
Root diseases, such as root rot, which is common in tomatoes, or even root infections in trees, are frequent causes of blockages when growing in soil or pots with poor drainage.
The main causes are usually:
• Presence of pathogenic fungi in the soil (such as Pythium, Fusarium, Rhizoctonia).
• Poor drainage or overwatering.
• Compaction that prevents oxygen from reaching the roots.
• Use of contaminated or poor-quality substrates.
Common symptoms:
1) Brown, soft or foul-smelling roots.
2) Wilted plants despite adequate watering.
3) Slow or no growth.
How to prevent and correct nutrient lockout: keys to a healthy crop
Here we explain how to prevent this annoying problem and what to do if it has already occurred.
Prevention: your best tool against nutrient lockout
Preventing nutrient lockout starts long before the first symptoms appear. Here are the keys:
• Use aerated, quality-tested substrates that are free of pathogens.
• Avoid waterlogging: a good watering programme and good drainage are essential.
• Check the roots when transplanting or if you suspect a problem.
Atami substrates are designed with the ideal balance between air and water, helping to prevent root problems. Choose from our extensive catalogue according to your needs, some examples are:
• Bi Grow Mix: ideal for moisture retention in dry climates.
• Janeco-Light-Mix or High Porosity Cocos: perfect if you need more drainage or work in humid areas.
Other checks and actions to prevent nutrient blockage:
1. Regular pH and EC checks: measure regularly and adjust if necessary. Incorrect pH is one of the main causes of this problem.
2. Balanced fertilisation adapted to each stage of the crop: follow fertilisation guidelines according to the stage (growth, flowering, etc.) and respect the doses. Excess can cause negative interactions between nutrients.
3. Choose products that support living soils and healthy roots: biostimulants such as Rootfast or organic amendments such as Worm Delight help strengthen the root system and improve nutrient absorption.
4. Keep a growing diary: recording pH, EC, doses applied, symptoms and visible changes will help you identify patterns and correct errors in time. Check out this blog on how to keep your growing diary and get the most out of it.
Advanced tips:
• Alternate watering with plain water to avoid build-up.
• Perform preventive flushes on demanding crops.
• Practice crop rotation in soil to maintain a balanced substrate.
How to correct a nutrient blockage if it has already occurred?
If your plants show symptoms such as yellow leaves, burnt tips or stunted growth, it is important to act as soon as possible. It may not be a deficiency, but a nutrient lockout: the nutrients are there, but the plant cannot absorb them.
• Step 1: Detect the cause
Check the pH and electrical conductivity (EC), examine the condition of the roots and analyse whether there has been excessive fertilisation. A pH that is out of range, salt accumulation or damaged roots are common causes of nutrient blockage.
• Step 2: Wash the substrate
Water thoroughly with pH-adjusted water (between 5.8 and 6.2, depending on the crop) to flush out excess salts and restore balance. This step is essential to unblock access to nutrients.
• Step 3: Recovery time
Avoid fertilising for a few days and observe how the plant develops. The recovery time from nutrient blockage varies, but a few days is usually sufficient if detected early.
• Step 4: Gradual reintroduction
Reapply fertilisers gradually, in small doses, so as not to saturate the medium again. Accompany with products that support root regeneration and improve absorption.
• Step 5: Soil recovery
In soil crops, incorporate organic matter, mature compost or Worm Delight, which improve soil structure and reactivate its beneficial microbiota.
In summary
Nutrient blockage is not always visible to the naked eye, but its consequences can completely halt the development of your plants. Detecting it early, understanding its cause and acting wisely makes the difference between a mediocre harvest and a top-quality harvest.
Remember: the problem is not always how much you give, but how much your plant can absorb.
Want to avoid blockages and improve your results?
Work with balanced products that care for the soil and roots from day one.
Explore our range of Atami fertilisers, substrates and biostimulants and grow without blockages, from the root.
