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What Is Nutrient Lockout and How Does It Affect Cannabis?

August 7, 2017

Nutrient lockout, also called “nutrient lock,” occurs when your cannabis plant cannot take up the nutrients that are in the soil. There are two primary causes of nutrient lockout:

  • Your cannabis garden is oversaturated with nutrients, particularly chemical fertilizers with a high salt content
  • There are unsuitable pH levels in the soil, water, or nutrient solution
What are the best nutrients for growing cannabis?

Once your plants are experiencing nutrient lockout, you’ll need to act quickly to reverse it and free the nutrients. Otherwise, they will become nutrient deficient and begin to die. To protect your plants, you’ll need to know how to identify nutrient lockout as well as how to correct, or better yet, prevent the issue altogether.

How to Identify Nutrient Lockout Signs and Symptoms

Identifying nutrient lockout can be difficult. Your cannabis plants may look underfed when in fact the problem is being created by overfeeding, pH variations, or other stresses on the plant.

Nutrient lockout will resemble nutrient deficiency; the plants will be weak and flimsy with stunted growth. Any yellowing or curling of the leaves also indicate that the plant is experiencing nutrient lockout.

Diagnosing Cannabis Nutrient Deficiencies in Sick Plants

When identifying nutrient lockout, first check the pH of the soil, water source, and nutrient solution. Generally, you want the pH for hydroponics to be between 5.5 and 6.5 and 6.0 to 6.8 for soil. When the pH is too high or too low, nutrient availability plummets and your plants cannot absorb the nutrients.

If pH isn’t the issue, take inventory of your plant’s nutrient diet. Have you been feeding your cannabis heavily? If so, try flushing your plants to free up the nutrients.

How to Fix Nutrient Lockout With a Flush

Once you have identified nutrient lockout, the first step is to stop feeding the plants. Next, flush the plants and growing medium accordingly with water. Flooding your pots with fresh, pH-balanced water or running a fresh solution in your hydroponic setup will help to break down and free the salt buildup and clear up the pathway for nutrients to be absorbed by your plants again.

How and when to flush cannabis plants

If nutrient lockout is an issue with your pH, consider using products to control your pH level. Purchase pH buffers to raise or lower the pH level and then flush with this pH-balanced water.

Once a flush is performed, your system will be completely saturated. The soil needs to dry out before watering again to allow the roots to breathe and avoid developing root rot. After a flush, you may continue to water your garden normally for a few more cycles before introducing nutrients again.

How to Prevent Root Rot, Mildew, and Leaf Septoria on Cannabis Plants

How to Prevent Nutrient Lockout in Cannabis

Prevention is always easier than correction, and there are a number of ways to prevent a nutrient lockout in your garden.

Check pH Levels Regularly

If you’re growing in a hydroponic setup, you should generally check your pH multiple times a day. It’s easy to monitor and correct nutrient lockout simply by adding pH buffers.

With soil, check the pH of both your water source as well as your soil. Based on your findings, you can use pH Up or pH Down, or top dress soils with lime (pH up) or sulfur (pH down).

What Is Hydroponics? An Overview of Soilless Growing

Use Organic Nutrients

Chemical fertilizers are salt-based, and these high salt concentrations tend to cause nutrient lockout. Look for nutrients with a low salt content or stick to organic nutrients exclusively.

Organic vs. Chemical Cannabis Fertilizers for Your Grow

Flush Your Cannabis Plants

When you are feeding heavily, take the time to flush your garden a few times during a grow. Your plants will appreciate the fresh water and a break from feeding, and they will respond magnificently when the nutrients are reintroduced.

Nutrient lockout is a problem that can be remedied as long as you’re paying close attention in your garden. Keep logs of your feeding schedule, observe your plants daily, and record what you notice before and after feedings. Cannabis plants respond rapidly to changes in their environment, which often makes them easy to care for under the eye of a vigilant, observant gardener.

Trevor Hennings's Bio Image
Trevor Hennings

Trevor is a freelance writer and photographer. He has spent years in California working in the cannabis industry.

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