Visual Guide to Foliar Symptoms of Nutrient Deficiencies in Cannabis
Professor DeBacco

Research Article
Llewellyn, D., Golem, S., Jones, A. M. P., & Zheng, Y. (2023). Foliar symptomology, nutrient content, yield, and secondary metabolite variability of cannabis grown hydroponically with different single-element nutrient deficiencies. Plants, 12(3), 422.
https://www.mdpi.com/2223-7747/12/3/422

General Reminders
Nutrient Mobility in the Plant
Mobile nutrients- Move to new growth areas
Deficiency symptoms will be seen first in the older leaves
Immobile Nutrients- Do not move to new growth
Deficiency will first be seen in the new growth

Nutrient Classifications
Primary Nutrient- (N-P-K): contribute to plant nutrient content, function of plant enzymes and biochemical processes, and integrity of plant cells. 
Secondary Nutrients- (Ca, Mg, S): Are needed in smaller amounts than primary nutrients
Micronutrients- Necessary for plant survival, but needed in small quantities

Fertilizers
Chelated preferred, since it will enhance nutrient uptake and improve efficiency of utilization. 
Goal is plant available nutrients


Nitrogen (N) Deficiency Correction
Primary and Mobile nutrient
Use 100-120ppm of Nitrogen Fertilizer as a target concentration
Nitrates vs Nitrates
Nitrates "dissolve" in water and, therefore, move about in the soil with the movement of soil water.
Nitrite is not a stable intermediate and is not able to be used by the plant.
Ammonia vs Ammonium
Ammonia has the highest N content of any commercial fertilizers (82%), however it is delivered as a gas and needs to be injected 4-8inches (10-20cm) below the surface. Here it will react with soil water to form Ammonium which can be used by the plants.
Calcium Nitrate is recommendation
Other Options:
Blood meal
Bat Guano
Urea
Like nitrates, urea dissolves in and moves with soil water and thus can be lost through leaching if not converted to ammonia and then ammonium. The conversion to ammonia takes only 2 to 4 days when soil moisture and temperature are favorable for plant growth. Lower temperatures slow the process, but it will continue even down to freezing.

Phosphorous (P) Deficiency Correction
Primary and Mobile nutrient on plant (generally immobile in soil)
Phosphites vs phosphates
Phosphates- Essential for plant growth and health
Phosphites- Not essential nutrients and used more as a fungicide that can induce the systemic acquired Resistance (SAR) in plants and is not a fertilizer.
Not a common deficiency that is seen in plants
Most growers over fertilize with Phosphorus especially when it gets to the flowering stage of their plants even though growers do not realize this because the toxicity symptoms are not easily seen.
Reason for not over fertilizing…
Keep nutrients in balance (maximize yields)
Save money
Limit potential for ground water contamination

Potassium (K) Deficiency Correction
Primary and Mobile nutrient
0-0-50 Sulfate of potassium
0-0-60 Potassium chloride
More potassium, but also more salt, typically used on large outdoor field applications
Wood ash can be used, but use it sparingly or your pH will increase dramatically

Calcium (Ca) Deficiency Correction
Secondary and Immobile nutrient
If you add lime there is calcium in this product but not much is plant available
Cal-Mag from Botanicare
Bio-min calcium

Magnesium (Mg) Deficiency Correction
Secondary and Mobile nutrient
Cal-Mag can have some Mg in it, but Epsom salts has higher concentrations of Mg
1 TBS/gallon (or 1 TBS/3.7L) for early onset and foliar applications
Substrate drench and foliar application suggested
2 TBS/gallon (or 2 TBS/3.7L) for a quickly progressing issue
This is a substrate drench rate, a foliar application at lower concentration (1 TBS/gallon) is recommended to reduce the chance of leaf burn

Manganese (Mn) Deficiency Correction
Manganese Sulfate
Often branded as Palm tree fertilizer
Age Old Grow
While the label only states Mn at 0.05% remember these are guaranteed minimums and based on tissue tests the likely actual concentration is much more.

Sulfur (S) Deficiency Correction
Secondary and Immobile nutrient
Adding elemental sulfur or sulfuric acid (battery acid) will add S, but it will also drive down your pH dramatically
Potassium sulfate (0-0-50)
Gypsum

Iron (Fe) Deficiency Correction
Micro and Immobile nutrient
Plant available forms are important as adding iron nails or filing will increase iron, but it is not plant available
Chelated forms are important for this nutrient
Bio-Min iron
Ferrous Iron sulfate

Link to Lecture Slides: https://drive.google.com/file/d/1UBrd...

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