The term N-P-K is often thrown around like they are the ABC’s of nutrients, which in a way they are. These three nutrients provide the foundation for what plants need to thrive. Using a prepared N-P-K mixture is similar to popping a multivitamin. This strategy provides the basics (allowing your plant to survive), but it really does not respond to the specific nutrient needs of your growing environment without manipulation. No two growing situations are identical.
Lighting, growing medium, cultivars, and stage of growing are all factors that will have an effect on the amount (and type) of nutrients that are needed. So instead of tossing in a generic formula, why not give the cannabis plants exactly what they are missing?
In this piece, we are going to explore two of the more critical nutrients: Nitrogen (N) and Phosphorus (P), and how they alter the development of cannabis.
How much is enough? And can there be too much of a good thing?
Nitrogen (N) plays many roles in the cannabis plant including aiding with the overall metabolism, building protein, chlorophyll and nucleic acid synthesis. This valuable mineral is a critical part to photosynthesis, root development and overall plant growth. In addition, nitrogen helps take in and transport other plant minerals throughout the plant. Understanding the amount of available nitrogen for the cannabis plant is critical to help regulate the overall growth of the plant. So, what is that level that will help ensure that your cannabis plants get exactly what they need?
PUT IT TO THE TEST
Saloner and Bernstein (2020) wanted to discover how the cannabis plant responded to nitrogen supply in the vegetative growth phase. Their study involved growing plants in different ranges of nitrogen levels ranging from 30mgL up to 240 mgL to determine what the optimal level of nitrogen was.
Their results revealed that cannabis plants showed signs of nitrogen deprivation when the available levels were less than 80mgL. Nitrogen deficiency resulted in restricted growth and development and leaf chlorosis, including the cannabis plants struggling with being able to produce lower stem radial growth, side branch elongation, and healthy root biomass accumulation. In addition, not enough nitrogen in the plant cells, resulted in restricted cell metabolism, a reduction in most of the plant processes and developmental delays.
What was interesting is that the plant reacted similarly when the levels of nitrogen were too high, over 160 ml/L, including a decline in photosynthesis levels resulted in stomatal closure and reduction in stomatal conductance, transpiration rate and intercellular carbon dioxide levels. Once the supply of nitrogen exceeded 240 mg/L, the root development became restricted, and at high levels, 320 ppm, the plant showed signs of a nitrogen overdose including smaller plant and plant organs and a dark green colour.
Their research revealed that the optimal nitrogen levels for a typical cannabis plant appear to be between 80 mg/L to 160 mg/L. This is when the plant showed positive growth, overall morphology (side branch elongation and healthy root biomass), and coloration, with optimal leaf, shoot and root development.