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Cannabis crops need nutrients and minerals that support their essential life functions. When the plants cannot take up the nutrients for one reason or another, they experience nutrient deficits.
Nutritional deficiencies in plants often manifest as leaf discoloration, blemishes, and malformation. Unfortunately, unseasoned cannabis farmers have difficulty distinguishing between cannabis deficiencies; high quality cannabis seeds caused by a lack of specific nutrients.
Therefore, it's essential to learn how to distinguish among the malnutrition signs resulting from specific mineral deficiencies and arrest the situation.
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Mobile VS Immobile Nutrients
Nutrient mobility influences the distribution and location of nutrients within the plant. For starters, mobile nutrient surplus deposits abound in the older leaves at the bottom of the plant; however, they move to the shooting area of the plant during a deficiency. The yellowing of leaves at the base of a plant indicates a mobile nutrient shortage. In contrast, immobile nutrients do not translocate to new growth areas during a deficiency, so yellowing at the shoot indicates immobile nutrients’ deficiency.
There are 14 minerals and non-minerals that play specific roles in the soil and plant to facilitate healthy plant growth. Plants need a more significant amount of macronutrients than micronutrients to thrive.
Macronutrients fall into two major subcategories:
Nitrogen, Phosphorous, and Potassium (N, P, K) –plants require them in large quantities.
Calcium, Magnesium, Sulphur (S, Ca, Mg)- plants utilize them in moderate amounts.
Besides these macronutrients, plants also need the micronutrients zinc, copper, boron, manganese, iron, chlorine, and molybdenum in tiny amounts.
Besides mineral deficiency in the soil or plant medium, a nutrient lockout may also impede nutrient intake in cannabis plants. Nutritional lockout occurs when plants cannot take up minerals via the roots, mainly due to overfeeding and pH deviation from the “sweet spot.”
Overfeeding results in nutrient saturation and salt buildup within the soil or plant medium; the salts come from chemical fertilizers. Consequently, the nutrients and salts may bond to form less absorbable compounds; some nutrients may also inhibit the absorption of other nutrients. On the other hand, pH alterations in the growth medium may be due to a change in your water’s pH or changes caused by the salt and nutrient build-up above.
Nutrient lockout manifests quite similarly to cannabis deficiencies as the leaves turn yellow while the crop exhibits stunted growth. However, it is not a nutritional deficiency and is also easy to arrest. First, check your water and soil pH and ensure they are within the 6.0-7.0 cannabis pH “sweet spot.” If not, consider flushing your crops with pH-neutral water to break down the salt buildup before resuming your herbs’ regular feeding schedule.
However, if the nutrient lockout is not the problem, nutritional deficiency is. So, let's examine cannabis deficiencies arising from insufficient micronutrient intake and how to tackle them.
Nitrogen is a mobile nutrient necessary throughout a cannabis herb’s lifecycle; it is particularly crucial during the vegetative stage for energy production. The compound’s physiological roles in plants include chlorophyll synthesis, photosynthesis, cell division for growth, and amino acid and protein synthesis. Nitrogen deficiency is most common in cannabis herbs during the flowering stage with the following symptoms;
Yellowing of older leaves at the base; the yellowing progresses upward from the bottom to shoot if the deficiency persists.
Phosphorus is a mobile macronutrient that supports photosynthesis, protein synthesis (especially DNA), and strong roots and stems development. Phosphorus is essential during cannabis germination but crucial for the flowering stage. Although phosphorous deficiency is rare, it occurs either due to low temperatures that hamper absorption or an increase in alkaline pH, showing the following symptoms.
Potassium is also a mobile macronutrient that facilitates carbohydrates and sugars transportation and plant’s water uptake. The mineral is also essential for photosynthesis, cell division, and energy production. Cannabis plants require potassium mainly during the vegetation and flowering stages. The signs of a deficiency include;
Similar to its bone-strengthening function in humans, calcium fortifies plant cells and facilitates strong root and leaf development. The immobile macronutrient also facilitates nitrogen and sugar transportation. Nitrogen deficiency is more common in hydroponic setups due to water, and its symptoms include;
Magnesium is a mobile nutrient crucial for chlorophyll synthesis, hence facilitates photosynthesis. It is also vital in synthesizing the necessary enzymes for sugar and carbohydrate production. Therefore, magnesium is crucial during the flowering stage, and its deficiency manifest as follows:
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Sulfur is an immobile macronutrient that facilitates fatty acid metabolism and is necessary for essential oils and terpene profiles. Although rare, sulfur deficiency may manifest as follows:
Cannabis deficiencies, if unattended, cause stunted growth and poor crop yield; fortunately, the deficiencies are pretty easy to correct. However, note the symptoms listed above carefully to ensure you are employing the correct fix for each problem.