Harvest is one of the most important parts of your hemp season. It is the…
This is a troubleshooting guide to help identify potential nutrient deficiencies while waiting for feedback from your state’s extension office or other identification service. Let’s take a look at the nutrients necessary for plant growth and development.
Primary/Macronutrients: Nitrogen, Phosphorus, Potassium
Secondary nutrients: Calcium, Magnesium, Sulfur
Micronutrients: Boron, Chloride, Copper, Iron, Manganese, Molybdenum, Zinc, Nickel
Micronutrients are often present in your water or soil (if applicable), however, micronutrient deficiencies can still occur, particularly iron. For this reason, water and soil should always be tested prior to planting.
As soon as you notice an issue with your plants, immediately note where on the plant it first occurred. For example, all anomalies in color, shape, and rate of development on what part of the leaf, what part of the plant (old or new growth). Where symptoms first begin is important to identification. Nutrient deficiencies often show up symmetrically on the leaf so if signs are asymmetric, the issue may be something else like disease or insect pests.
Next, check pH. Make sure the pH of your grow media, irrigation, and/or fertigation is properly regulated for your plant and nutrients. Often plants will exhibit signs of deficiency if pH is too high or too low, even when adequate amounts of nutrients are supplied because some nutrients aren’t available at certain pH levels. This is known as nutrient lockout.
The ideal pH for your cannabis grow will be between 5.8 and 6.0. Most necessary nutrients are available at different levels within this range so allowing fluctuation within the range helps to provide the highest nutrient availability possible.
Chlorosis – yellowing of leaf parts, can show up in different areas and patterns
Mobile – nutrient is able to move through the plant and will move from older tissue at base of plant to younger tissue at tops of plant
Immobile – nutrient does not move through plant, deficiencies shown in new growth
Partially mobile – Some mobility potential
Leaf abscission – leaf shedding
Necrosis – plant parts darkening and wilting, dying off, may appear as burning
Interveinal – space in between the veins of the leaves
Leaf margins – the edges of the leaves
See the chart below to identify specific symptoms and the nutrients they are associated with.
Nitrogen (N) - Mobile
Phosphorus (P) - Mobile
Potassium (K) - Mobile
Calcium (Ca) - Immobile
Magnesium (Mg) - Mobile
Sulfur (S) - Immobile/partially mobile
Molybdenum (Mb) - Partially mobile
Function: Helps plant metabolize and use nitrogen as urea, and assists in iron uptake
Deficiency Symptoms: Necrosis on leaf tips
Additional Notes: Essential for Fe uptake