The seed company Dinafem explores this issues in a lenghty blogpost, describing every single primary, secondary and micro- nutrient, pointing out are the characteristics that indicate an excess or a deficiency of a specific nutrients.
"Adequate lighting, proper ventilation, a good substrate and a balanced feeding regime are key aspects to growing great cannabis. The last point is probably one of the hardest to deal with, as it involves assessing the needs of the plants by just looking at them, and this, however necessary for proper plant development, often takes an expert eye."
"For instance, Nitrogen is essential during vegetative growth. Pitrogen plays a central role in the formation of leaves and stems, in chlorophyll production and in photosynthesis. Nitrogen deficiency can be spotted when older leaves near the base of the plant gradually yellow and overall plant development is delayed. Because it is a mobile element, nitrogen stored in older leaves can be used to solve a deficiency elsewhere in the plant. You can easily solve a nitrogen deficiency, bringing colour and vigour back to your plants, by watering with a nitrogen-rich, pH-balanced solution. On the other hand, a nitrogen excess can be seen when leaves turn glossy dark green, starting at the margins and spreading out until the whole leaf surface is covered. Tips curl down like eagle claws. To turn nitrogen excess around and get your plants thriving again, flush the substrate in a bathtub for about 15-20 minutes, leave it to dry and add enzymes with the next watering."
Read the full article at dinafem.org
