Understanding Cannabis Nutrition: Deficiency, Lockout, Toxicity? What Does It All Mean?

Nutrient lockout is a term that means the nutrients in your media or reservoir are unavailable to the plant.

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In order for nutrients to become bioavailable to the root, certain parameters must be met. If you are growing in excessively acidic or alkaline conditions, you will throw certain essential nutrients out of range causing lockout to occur. If lockout is not addressed through monitoring pH and EC, visible nutrient deficiencies will follow. 

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A common reason for lockout to occur is from an excess concentration of nutrients (solutes) in the growing media and/or reservoir solution. The salt build-up causes the pH to rise above the optimal range.

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New growers may try to treat the deficiency with more nutrients when the remedy is actually flushing the media of excess nutrients.  

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Each essential nutrient has a unique rate of absorption by the root in relation to pH. We recommend maintaining a pH between 5.8-6.3 when using Future Harvest products for maximum absorption rates of all 12 essential nutrients.

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It is best to try to maintain a steady pH without significant fluctuations in readings. To understand nutrient availability in relation to pH at-a-glance, nutrient availability charts can provide a good visual reference. 

 

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pH in Hydroponics Chart

 https://manicbotanix.com/ph-in-hydroponics/ 

 

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Diagnosis of possible nutrient deficiencies can be made a lot easier by understanding the concept of nutrient mobility. Mobile nutrients like nitrogen can be remobilized within the plant to send resources to newer growth when a deficiency is detected by the plant.  

 

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The symptoms appear in the older leaves lowest in the canopy, as chlorophyll is remobilized causing yellowing to occur. By knowing that mobile nutrients demonstrate symptoms in older growth first we can significantly narrow the possible causes of toxicity or deficiency based on the concept of mobility alone. Since immobile nutrients like iron cannot be mobilized, symptoms will appear on new growth first.  

 

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Mobile and Immobile Nutrients

http://fontanelle.com 

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If you think you have nutrient deficiency, follow these steps to make your diagnosis: 

1. If you are running multiple plants, check that all of the same strain with the same irrigation are displaying symptoms. If only one plant is symptomatic it could be pest or disease related foliar damage. It is best to eliminate the possibility of plant disease or pest infestation prior to taking any action. 


2. Test the pH of your irrigation water and your media. A pH between 5.8-6.3 should be maintained throughout your entire grow. Use the pour-thru or saturated media methods to test the pH and electrical conductivity (EC) of your media if you are a soil grower. Always make sure to calibrate your pH meters prior to testing.  

 

3. Are symptoms appearing at the base or top of the plant? Again, this will tell you whether your deficiency is mobile or immobile, which is fundamental to identifying nutrient deficiency symptoms.

    Old growth showing symptoms first = a mobile nutrient deficiency.

    New growth displaying symptoms = an immobile nutrient deficiency. 

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       Plant Nutrient Deficiency Key
      https://www.canr.msu.edu/ 

       

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      The next step in the process is to use a deficiency key (see above).  
        If you've followed a deficiency key but are still uncertain as to what your deficiency may be, it is wise to consult a trusted source, who can make a secondary diagnostic. If money or time are not a concern for you, one can send tissue samples to a reputable nearby lab for testing. 
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        Remember, you can always ask Future Harvest any growing questions you have!

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          It is important for new growers to note that deficiencies in cannabis can often be misdiagnosed by seasoned professionals. If you are using Future Harvest Nutrients as suggested by our online feeding schedules you should not see deficiencies. If you are seeing a deficiency, verify your pH and PPMs are correct.

           

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          These symptoms could also be the result of overfeeding, in which case the remedy is to flush your media of excess salts with Plant Flush and verify the dilution ratios of each of your nutrients.

           

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          Strain-specific genetics come into play in terms of dialing in your feeding schedule. For instance, one strain may be more nitrogen-loving than another, so it is our job to continuously monitor our crops for early symptoms of lockout, toxicity or stress.

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          The following are symptoms and remedies for deficiencies common to cannabis: 

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          Nitrogen Deficient Plant - Courtesy of our friends at GrowDoc App

          NITROGEN: Highly mobile, associated with leaves producing chlorophyll (green pigment) for photosynthesis.  

           

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          Deficiency symptoms: old growth yellowing (chlorosis), progresses up the plant if left untreated. Leaves will lose their photosynthetic function turning yellow and eventually die, leading to diminished yield and overall growth.  

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          Toxicity Symptoms: Leaves are dark green and curl in a claw-like fashion, weak stems, stunted growth.  

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          Treatment: If you are growing hydroponically, the best solution for low nitrogen levels is to start using formulas that provide all the necessary nitrogen a plant needs. Using Future Harvest's Holland Secret grow, bloom, and micro together in vegetative growth as directed by our feeding schedule, one should not see a nitrogen deficiency. Using Future Harvest's Calnesium, will also help increase nitrogen uptake and can be diluted as a foliar spray for immediate relief.  

           

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          For soil and coco growers, using a chelated mix like our Easy Plus series powdered nutrients, verify your the EC and pH of your media and water, as all of our products are designed to avoid deficiencies if you are using as directed by our feeding schedule. Because chelated nutrients are taken up by the plant at a slower rate than in a hydroponic solution, one should be very cautious increasing the amounts of nutrients beyond what our feeding schedule suggests, as it could lead to nitrogen toxicity or lockout as well. If you are experiencing toxicity, the remedy would be to flush with fresh water, remix a nutrient solution using calibrated pH & TDS (ppm) meters to verify nutrient availability, and keep a watchful eye as your plant recovers from toxicity.  

           

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          Organic growers can amend their soil using organic compost, blood meal, worm casting and fish emulsions, to name but a few.  

           

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          Phosphorous Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Phosphorous Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Phosphorous Deficient Plant - Courtesy of our friends at GrowDoc App

           

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          PHOSPHOROUS: Phosphorous deficiencies diminish a plant's ability to release stored carbohydrates for energy and hinder photosynthetic potential. A phosphorous deficiency can lead to low yields, less resin production during flowering and can delay flowering. Phosphorous is mobile so older growth will display symptoms first.

           

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          Deficiency Symptoms: Purple-coloured or bluish leaves and stems & black dead spots on leaves before affected leaves eventually die and fall from the plant.

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          Toxicity Symptoms: Toxicity is not likely to occur at a correct pH level, and is quite uncommon and takes weeks to show symptoms though excess phosphorous can potentially lockout other nutrients like iron, zinc, magnesium, calcium and copper. This lockout will produce symptoms of micronutrient deficiency.  

           

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          Treatment: Growers should adjust their pH levels, flush with pH adjusted fresh water, increase temperatures of their environment (phosphorous uptake is diminished at low temps), decrease frequency of watering and as a preventative measure, amend soil prior to potting to ensure a healthy amount of drainage. Phosphorous deficiencies can occur naturally in cold weather, compacted soils, overwatered media, as well as infestation and disease. Plants should bounce back in about a week's time after treatment, though affected foliage may not recover.  

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          Potassium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Potassium Deficient Plant - Courtesy of our friends at GrowDoc App

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          POTASSIUM: Potassium is another mobile nutrient responsible for transporting water and nutrients through your plant. Potassium is integral in water/nutrient uptake, transpiration, root production and cell division. A potassium deficiency increases the internal temperature inside the plant which causes excessive transpiration rates in order for the plant to cool down. Potassium deficient plants will be much more susceptible to disease and pest infestation. Potassium deficiencies are often the result of lockout from excess calcium and magnesium and can lead to a nitrogen deficiency due to lockout as well.

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          Potassium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Potassium Deficient Plant - Courtesy of our friends at GrowDoc App

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          Deficiency Symptoms: Distorted or curled leaves starting from the oldest growth in the sub-canopy. Deep dull-green lower foliage with burned tips, brown spots and interveinal yellowing. Symptoms will progress up the canopy eventually, and result in a weak plant with drastically diminished yields.

           

          Toxicity Symptoms: There is no-known toxic effect to excess potassium other than the effect excess potassium has on the availability of other nutrients (nitrogen, calcium, magnesium).  

           

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          Treatment: Flush the media with pH balanced fresh water and Future Harvest Plant Flush in suggested concentrations. Ensure Calnesium is not being used to excess by referencing a feeding chart. Calibrate all necessary meters and probes & remix your nutrient solution.  

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          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App

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          CALCIUM: Calcium is an immobile secondary nutrient responsible for the structural integrity of the plant, and aids in resilience to environmental stressors like excessive heat. Using reverse osmosis water can lead to calcium deficiency because there is no calcium present in the water already, as opposed to regular tap water. Calcium is found in abundance in soil, so soil growers need not be worried unless growing in extremely acidic soil.  Calcium deficient plants are much more susceptible to diseases like root rot.

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          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App 

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          Deficiency Symptoms: will present in newer growth first and foliage may have small dark spots on leaves as well as yellowing that begins from the veins of the leaves and spreads outward. The new leaves may grow distorted curled. Yellowing does not occur in every symptomatic plant but is a secondary symptom to watch for. The spotting or blotches will appear dark brown or rustic in colour.  

           

          Toxicity Symptoms: Calcium, like potassium, is non-toxic to plants, though excess calcium causes high pH levels that lock out other essential nutrients (potassium, magnesium, manganese and iron).

           

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          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Calcium Deficient Plant - Courtesy of our friends at GrowDoc App 

           

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          Treatment: Flush media with Future Harvest Plant Flush, add Future Harvest Calnesium to your regular feeding schedule in conjunction with Holland Secret Grow/Micro/Bloom. Verify optimal pH and ppm ranges of your reservoir. Stop feeding with RO water if possible. Future Harvest Organical Magic is essentially organic-certified Calnesium for soil growers, so those growing organically should use Organical Magic, instead of Calnesium.  

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          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

           

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          MAGNESIUM: Magnesium is a mobile secondary nutrient, the core of chlorophyll molecules (green pigment) and serves many essential enzymatic functions. Magnesium deficiency symptoms present in oldest growth first.

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          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Magnesium Deficient Plant - Courtesy of our friends at GrowDoc App

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          Deficiency Symptoms: interveinal yellowing progressing up the canopy, yellowing occurs from the center of the leaf out toward the margin. Leaves may also curl in an upward direction. Magnesium can also be flushed from media due to overwatering. Using bloom fertilizers in excess can cause high levels of phosphorous and potassium that can lead to magnesium lockout.

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          Toxicity Symptoms: Toxicity is very rare, though it can occur by interfering with calcium uptake. A magnesium toxicity will display the same symptoms as a calcium deficiency. (See above) 

           

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          Treatment: Flush media with Future Harvest Plant Flush, add Future Harvest Calnesium (Organical Magic for organic growers) to your regular feeding schedule in conjunction with Holland Secret Grow/Micro/Bloom. Verify optimal pH and ppm ranges of your reservoir. Cut back on bloom formulation concentrations in your reservoir. Verify humidity and temperature in your growing environment are within optimal ranges.  

           

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          Iron Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Iron Deficient Plant - Courtesy of our friends at GrowDoc App

          IRON: Iron plays roles in leaf pigment, respiration and is involved in enzyme production within a plant. Iron is most readily-available to a in ferric form, though it can be absorbed organically as well. Iron deficiencies are usually the result of pH fluctuation. A pH above 7.0 will lead to iron deficiency through lockout.  High levels of salt content in the media, too much moisture, and excessively high or low temperatures will also affect iron uptake.

           

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          Deficiency Symptoms: will appear in new growth first and include: Yellowing of young leaves, though veins remain darker shade of green. Similar symptoms to magnesium deficiency (see above), but occurring on young foliage. New growth may be distorted or lack leaflets. Chelated forms of iron are integrated into Future Harvest formulations to prevent iron from oxidizing out of your water in a non-soluble form. Iron deficiency is rare in soil but can occur due to an abundance of calcium and/or bicarbonate causing iron lockout in an overly-alkaline soil.

           

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          Toxicity Symptoms: will be the same as deficiency symptoms for various other micro-nutrients because excess iron causes lockout of other nutrients.  

           

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          Iron Deficient Plant - Courtesy of our friends at GrowDoc App

           

          Iron Deficient Plant - Courtesy of our friends at GrowDoc App

           

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          Treatment: As a preventative measure, make sure media has proper drainage aerated prior to potting. If deficiency or toxicity symptoms appear, flush media with Future Harvest Plant Flush, verify optimal pH and ppm ranges of your reservoir. Re-calibrate environmental controls. (Humidity, temp, etc.) 
           

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           Sulphur Deficient Plant - Courtesy of our friends at GrowDoc App Sulphur Deficient Plant - Courtesy of our friends at GrowDoc App

           

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          SULPHUR: Sulphur aids in chlorophyll production, protein production, enzymatic functions and the synthesis of essential resins and oils. Plants deficient in sulphur during flowering may see their flowers die if left untreated. Sulfur deficiency is rare however, as plants can derive sulphur from the atmosphere through the stomata. Future Harvest formulations provide sulfates in carefully formulated concentrations to avoid toxicity and deficiency with proper use.  

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          Deficiency Symptoms: yellowing similar to that of Nitrogen but occurring in new growth as Sulphur predominantly mobile. The yellowing is unique however, in the sense that it occurs from the base of the leaf outward. Sulphur deficiencies can also cause discoloration on the underside of the leaf with pigments of pink, red or orange. 

           

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           Sulphur Deficient Plant - Courtesy of our friends at GrowDoc App
           Sulphur Deficient Plant - Courtesy of our friends at GrowDoc App

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          Treatment: If deficiency or toxicity symptoms appear, flush media with Future Harvest Plant Flush, verify optimal pH and ppm ranges of your reservoir. Re-calibrate environmental controls (humidity, temp, etc). Those that work in commercial facilities are accustomed to sulphur burns to provide sulphur in the atmosphere and help aid in powdery mildew control. These applications are much better suited to the commercial market, however, because sulphur burns require a 24-hour period to elapse before re-entry of cultivation personnel to the greenhouse growing environment is considered safe.

           

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          MANGANESE: Manganese contributes to many biological functions such as: photosynthesis, respiration, pollen germination, root cell growth (elongation of cells). It also helps protect against root diseases. Manganese is immobile so the first symptoms of deficiency or toxicity appear on new growth. Manganese becomes unavailable to a cannabis plant at a pH above 6.0.

           

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          Deficiency Symptoms: will include young leaves demonstrating interveinal yellowing and eventually brown spots or blotches that can progress to kill the leaf. Like sulphur, the yellowing will occur at the base of leaf progressing outward.  Deficiencies of manganese, though rare, are most commonly caused by high pH and an excess of iron in your media or reservoir.

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          Toxicity Symptoms: Manganese toxicity occurs due to highly acidic growing conditions, plants with low levels of silliates or deficient levels of calcium.  

           

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          Treatment: If growers use Holland Secret Grow or Bloom in conjunction with our Micro formulation, they will not see manganese deficiency or toxicity. If it does occur perform a flush, calibration and test for pH and dilution concentrations as mentioned previously. Similarly, our Easy Plus series of powdered nutrients deliver all micro-nutrients at carefully developed ratios that cannabis requires including, manganese.  

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          Our friends at GrowDoc App teamed up with Niagara College to study the effects of nitrogen, potassium, and phosphorus deficiencies on cannabis plants!

           

          The studies were completed with two different strains, Shishkaberry, and Cold Creek Kush. These were then stripped of either nitrogen, phosphorus, or potassium and then compared to a control plant. 

          They began NPK deficiency studies with Niagara College in late May of 2021 with the goal of gaining information on the effects all three deficiencies have not only on the cannabis plant but the cannabis itself. With this new report coming back from the lab we can see exactly how each deficiency affects the amount of THC and cannabinoids.

           

          Some of the standout results of this study were:

           

          • Up to 28% DECREASE in THC

          • Up to 25% DECREASE in Terpenes

          • Up to 96% DECREASE in Yield 

          • UP to 50% DECREASE in Height

           

           

           

          Diagnosing specific nutrient deficiencies is a skill that can take years to develop. Since nutrient formulations come in pre-mixed ratios of all essential nutrients, the remedy in most cases is to flush, calibrate and remix your solution. Chances are that pH and the ratios of total dissolved solids in your solution are out of range if your plant is displaying deficiency or toxicity symptoms. A quality pH and EC/PPM (and calibrated) meter is paramount to properly monitoring your crop, such as the Growboss by Nutradip. Nutradip offers calibration solution for their probes as well.  

           

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          If you want to check the health of your plant or to detect a deficiency or toxicity, there's an app for that! You can check out the GrowDoc app HERE When it comes to plant health, prevention is always better than reactive treatment. Understanding the characteristics of your genetics, potential pest and disease issues, optimal environmental conditions, your growing media characteristics, and adhering to the dilution ratios provided by your Future Harvest feeding schedule will go a long way in maintaining a healthy plant from seed to harvest.  

                                                                          

          Any questions? Email us at marketing@futureharvest.com or send us a message on Instagram @futureharvestdevelopment and we will help you as best we can!

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            Published by Future Harvest

            Bio:
            Future Harvest | Grow Better |

            E-Mail: marketing@futureharvest.com

          • Mar 03, 2022
          • Category: Articles
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