Nutrients
Nutrients can broadly be categorized by micro or macro and in terms of their mobility; either mobile or immobile. Mobile nutrients are those that the plant can move around to where they are most needed while immobile nutrients cannot be relocated. This mobility of the nutrient affects where symptoms of deficiency (or excess) can occur on a plant.
Macro Nutrients
Macronutrients are those nutrients that Cannabis requires in large amounts, the three main nutrients are Nitrogen, Phosphorus, and Potassium (often written as NPK). They typically come from the soil and are crucial throughout the plant's lifespan, although in differing ratios. Vegetating plants require more Nitrogen and less Phosphorus and Potassium, while flowering plants demand much less Nitrogen and much more Phosphorus and Potassium during the flowering stage. A rough guide NPK ratio:
| Stage | N | P | K |
| Vegetative stage | 3 | 1 | 2 |
| Flowering stage | 1 | 1 | 2 |
| Final Flowering Stage | 0 | 1 | 2 |
Nitrogen
Required for the production of most plant cells as well as chlorophyll, used in photosynthesis.
Phosphorus
Essential for the flowering period, Phosphorus strengthens the plant and is used for root development.
Potassium
Required for root development. Potassium also regulates the opening and closing of stomata for gas exchange.
Cannabis also obtains Oxygen, Carbon, and Hydrogen from water and air.
Micro Nutrients
Silica
Silicon dioxide or "Silica" can increase stem diameter and boost chlorophyll production.[1]
Magnesium
A mobile nutrient required for the creation of chlorophyll in a plant, a requirement of Photosynthesis.
Calcium
An immobile nutrient that is required for the creation of strong cell walls.
Boron
Similar to calcium, boron is required for strong cell walls.
Copper
Copper is used in photosynthesis by helping metabolize proteins and carbohydrates.
Iron
Iron supports the function of chloroplasts.
Manganese
Sulphur
Zinc
The sequence of nutrition
The biochemical sequence depicts the order in which nutrients are required by the plant and the interconnections between nutrients.
Nutrient antagonism
High concentrations of one nutrient can decrease the bioavailability of another, this is known as nutrient antagonism. For example, high Nitrogen will decrease the availability of Boron.
Deficiencies
Most deficiencies present as a color change on the leaves, moving from the center outwards or from the edge of the leaf moving inwards. Deficiencies can appear on older leaves first or newer leaves first. Mobile nutrient (such as NPK) deficiencies will show on older leaves first as the plant moves nutrients to the younger leaves. Deficiencies will remain in leaves that have already finished growing even after it is remedied in fresher leaves. This means you must be patient in remedying mobile deficiencies
Nutrients can be added to the growing medium before planting if possible, to avoid deficiency.
Nutrient lockout
Nutrient lockout occurs when the pH is too high or too low for the plant to properly absorb nutrients. This leads to a deficit of necessary nutrients for growth and/or survival. A nutrient lockout can also occur when the grow medium accumulates too much salt or other nutrients.
Pre-mixing nutrients
If you intend to mix nutrients in water in large quantities and leave it to sit for a period of time one should consider the nutrients used and how they may change over time. When mixing organic nutrients in water they will respire aerobically for a period of time, until they run out of oxygen and then begin to respire anaerobically. This destroys some of the bacteria's capabilities and makes for a less effective feed. The water will begin to smell like a pond or an asshole when the bacteria begin to respire anaerobically which is a surefire way to tell. Synthetically derived nutrients may last longer in water but can also become less effective as some nutrients may combine to create less accessible forms of the nutrient for the plant.
Methods of Nutrient delivery
Via growing medium
The most simple method of nutrient delivery is by mixing with the water to be used for watering the cultivar. Take note that the growing medium will affect the stability of the pH in the plant's root zone. Organic soils provide more of a pH buffer than hydroponic systems because, in organic soil, there are other organisms that help regulate pH. Even though nutrients have been added to the growing medium they will not be bioavailable to the plant instantly. Other organisms help in the process of breaking down nutrients so that they are useable by the cultivar, such as Mycorrhizal Fungi.
Foliar Spray
Nutrients can be delivered to the plant when dissolved in water via a fine mist, this is the fastest route of administration. It has been postulated that the size of the droplets has an effect on the efficacy of foliar spray but some studies seem to contradict this[2]. If possible the spray should be applied to the underside of leaves as this is where most stomata reside. Lights should be turned off before foliar spraying to prevent the light lensing through droplets burning the leaf surface. Foliar spray should not be used to provide emergency nutrients to the plant.
Sources of nutrients
Nutrients can be provided to a cultivar via concentrated liquid solutions, dry amendments, organic materials, and even other organisms living in the growing medium.
Liquid fertilizer solutions can roughly be broken into two categories: those for the vegetative stage and those useful in flowering.[3]
If you are trying to provide NPK organically you can check the NPK values of most organic materials at thenutrientcompany.com
References
- ↑ https://www.maximumyield.com/simply-silica/2/1077
- ↑ Influence of Droplet Size of Foliar-Applied Nitrogen on Grain Protein Content of Hard Red Winter Wheat 2017 -https://acsess.onlinelibrary.wiley.com/doi/pdf/10.2134/cftm2016.10.0068
- ↑ https://www.hydrostork.com/npk-fertilisers-types-roles/