The Quick & Dirty Nutrient Deficiency Guide

Cannabis Nutrient Deficiencies: 

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Please note that his article was written with hydroponic cannabis in mind, if you are growing another type of plant in other circumstances, much of this would not be relevant to your situation.

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If you search plant nutrient deficiencies on the internet you'll be bombarded with hundreds of results. This can be confusing for many growers, newbies or veterans. Some articles on plant deficiencies are on an academic level, while most are a simple copy and paste of "Nitrogen: Yellowing showing up first in the older leaves". 
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Most deficiencies look similar and even professionals have a hard time diagnosing them. Most of the time, professional growers don't even rely on symptoms. Instead, they send leaf samples to a lab for analysis and proper diagnosis. 
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Regardless of the manufacturer, hydroponic fertilizer should be a complete nutrition formula - meaning that if used correctly, there should never be issues with deficiencies. 
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We don't want to add to the confusion by providing you with another list going over what deficiencies look like. 
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So we are going to address the most common issues our customers call and email us about!
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Phosphorus Calcium

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By far the most common problem we see is when growers have too much Phosphorus or Calcium and a reaction happens which locks out their availability. 
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This usually shows up as a calcium deficiency but the lower levels of phosphorus will also have an impact on yield. 
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This is characterized by an all around unhealthy, stunted plant, with yellow brown spots on the leaves.  

 

This can be easy to check: simply leave a sample of nutrient solution sitting out for a day or two. If there's white sediment in the bottom then it will likely be from this type of lockout. 
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For the next step you'll want to check your water source. Check the TDS using a meter - ideally it should be as low as possible. Most of the time this reading is due to calcium dissolved in the water which can potentially mess up the nutrient solution. Starting at around 200 PPM there is potential for this to happen. 
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If this reaction is occurring, then our Holland Secret Hard Water Micro should be used. It contains 1% calcium rather than the 5% in the regular Micro. 
You are safe to use a CalMag supplement, but once the PPM starts to approach about 350 we recommend you leave that out as well. 
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Another option is to lower the phosphate levels by decreasing PK supplements by 20% - we recommend you consider lowering calcium levels first. ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

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Iron:

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Of all the essential nutrients, iron is the most chemically unstable. This means it can easily be oxidized which causes it to fall out of solution.

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An iron deficiency is characterized by younger leaves staying green in the veins but yellowing in the remainder. 

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Low magnesium will show up with similar symptoms so you have to perform a test to confirm which deficiency your plant is suffering from. Leave a sample of nutrient solution out for a day or two. If there's a brown-red fallout (rust) then the plant is likely not getting enough iron. 
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High pH (6.8+), too much oxygen, and iron oxidizing bacteria (appearing as a brown gelatinous slime) are the causes of this deficiency from a fallout. 
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If you have an abundance of oxygen, either through air stones or Hydrogen Peroxide, try cutting back. 
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Although rare, if there appears to be iron oxidizing bacteria then add Hydrogen Peroxide at a rate of 2 mL per liter. 

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pH

Feeding programs by any reputable manufacturer will be nutritionally complete and your plant shouldn't have any deficiencies while following the feeding schedule.
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Often times when deficiencies occur, it is because of something going wrong while feeding the plant. Besides the others I've mentioned, pH levels can potentially cause a lot of problems. While we normally recommend aiming for a narrow window of 5.8 to 6.2, others have stretched these numbers out a bit with positive results. However, going over 6.7 could cause multiple nutrients to lockout: phosphorus, iron, manganese, and boron. With a nutrient lockout like this, there could be symptoms form multiple deficiencies making diagnosis a nightmare. 
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Simply monitor the nutrient solution closely and adjust accordingly. 

 

 

Final Thoughts:

After years of customer calls about sick plants, these seem to be the most common issues. If you follow these recommendations, you should be able to remedy the vast majority of problems. We always recommend you do some research first before coming to us so you can provide us with the most accurate knowledge about your plant and what you think is wrong with it. Having a starting point will help us get to the bottom of your issues. We are happy to help with any possible deficiencies, whether that be some of the more common ones we mentioned, or something different like low sulfur or zinc!

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For growing help, product questions, or any other inquiries please don't hesitate to contact us!
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Call us at 250-491-0255 (Local) 866-491-0255 (Toll Free North America) 
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Email us at marketing@futureharvest.com
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Reach out to us on Instagram at @futureharvestdevelopment 

    Published by Loren Price

    Bio:
    Loren, the Director of Fertilizer Technology at Future Harvest, grew up on a mixed grain and cattle farm in North West Saskatchewan. He went on to study biotechnology and worked in agrosciences in Saskatoon for several years before moving on to Future Harvest and the hydroponic plant food industry. Starting off in fertilizer production, his focus is now on fertilizer formulations and regulatory affairs. His areas of expertise include: agronomy, analytical chemistry, plant tissue culture, plant breeding, molecular biology, and plant nutrition. Outside of work, Loren collects vintage concert T-shirts and is an amateur craft brewer specializing in historical and lesser known styles of beer.

    E-Mail: loren@futureharvest.com

  • Jul 13, 2020
  • Category: Articles
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