Plant health

How to recognise and fix nutrient burn

By Michelle Joe on September, 9 2021
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Michelle Joe

Michelle is a creative copywriter and storyteller who loves to connect brands with their audiences. She enjoys being a part of Bluelab’s innovative growing journey.

Nitrogen and other nutrients are essential for plant growth; however, it is possible to overdo it. This is what you call a ‘nutrient burn’ and is a common growing issue that is easy to rectify if caught early on. It can be frustrating to see your plants struggling while you learn how to give them the best care. Learning the signs, causes and treatment for nutrient burn will help you prevent crop losses in the future.

Let's address some common questions you might have about nutrient burn so that you can begin your research journey.  

What is nutrient burn? 

A cannabis leaf showing signs of nutrient burn

The most common cause for nutrient burn is when growers overfeed their plants with bottled nutrients in a controlled environment. Plants can't get rid of the excess nutrients so the nutrients unfortunately cause root and leaf damage. When there is leaf damage, or burn, it reduces the available surface area for photosynthesis to occur. As a result, your plants will produce less glucose that is required for optimal growth. 

If plants are left unchecked, nutrient burn can cause leaves to die completely and fall off the plant. For cannabis growers, it is important to address nutrient burn to protect crop yields. For crops like lettuce and tomatoes, the nutritional value can decrease as a result of nutrient burn.

Signs of nutrient burn on leaves

It is key that you know the earliest signs of nutrient burn so you can rectify the situation earlier on in order to prevent crop loss.  Visual signs to look out for are:

  • Leaf tips are bending or curling
  • Leaf tips turn yellow or brown—the plant is trying to get rid of excess nutrients and sends them to its furthest reaches 
  • Leaves turn an extreme or oversaturated deep green colour—this indicates over fertilisation

How to fix nutrient burn

Regardless of crop type, ensure that you are giving your plants the right nutrients depending on where they are in their life cycle. Plants need different nutrients in their vegetative and flowering stages, so feeding them the wrong fertiliser at the wrong time can cause nutrient burn. 

Read fertiliser labels carefully, and learn how to add the correct amount of nutrients. 

Growing in soil:

If you hand water your plants and notice nutrient burn, cut the affected foliage and flush your plants with plain pH-balanced water. Flushing removes the excess nutrients from the soil and will help your plants recover. You can test the pH of your water with a pH pen and adjust your nutrient solution.

Growing hydroponically:   

You can dilute the nutrients in your system with plain pH balanced water—test the pH levels with a pH pen. If you realize that you are giving the plants the wrong nutrients, you can completely change out the water and start over with the proper fertiliser at the right dilution level. You can use a Truncheon Meter to monitor the level of nutrients in your water. 

How to prevent nutrient burn    

In order to grow healthy plants and prevent nutrient burn, you need to create the right pH levels for your crops. Each crop prefers a specific pH range and will flourish when the soil, or growing medium, has its favourite pH level. For example, cannabis grown in soil loves a slightly acidic environment at its roots. 

If the pH level is outside of a plant’s range, then it cannot take up the nutrients added to the soil or hydro system. You may make the mistake of adding more fertiliser to remedy an ailing plant when the root cause is an incorrect pH level. Not only are you investing in fertiliser that the plant can’t use, but your crop yields will also be lower because your plants are not thriving.  

You can remedy this by monitoring the pH levels of your water and soil with reliable tools like a Soil pH Pen Measuring conductivity (EC/PPM) with an EC meter is another way to know if your plants can take up nutrients properly.  It’s best to take action based on the data you gather from regular pH and EC testing.

 

Will plants recover from nutrient burn?  

Nutrient burnt leaves will not turn green again, however, you can clip the burnt bits off. The key indicator that your recovery methods are working is if the burning stops in its tracks. If whole leaves are burnt to the point of dropping off the plant, make sure to remove them so they don’t create a haven for pests. 

If the nutrient burn is severe, it might make more financial sense and save you time in the long term to restart your grow.

How to tell if it's nutrient burn or a nutrient deficiency

It can be difficult to figure out the difference between nutrient burn or nutrient deficiency in plants. For example, potassium deficiency causes cannabis leaves to yellow on the margins and turn brown on the edges. This is similar to what nutrient burn looks like in cannabis.  

One way to diagnose your plants is to find out if the growing environment has a pH issue. Nutrient deficiencies are usually caused by the wrong pH level. You can regularly test your plants’ run-off to see if the pH level is within the desirable range. If the pH level is correct, then you are likely looking at nutrient burn. 

Back to the healthy plant basics 

Balancing nutrients and feeding is one of the harder parts of growing, but once you get it right, nutrient burn will become a thing of the past. 

Measure your pH and EC/PPM levels often. It’s the best way to reduce the “what if’s” of growing healthy crops and sleep soundly with easy, reliable data collection.

 

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