Nutrient Delivery

what nutrients do cannabis plants need?

The most important nutrients for cannabis plants are Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and Sulphur (S).

Nitrogen promotes plant growth during the vegetative stage, phosphorus helps to develop flowers, potassium will promote a dense bud growth, calcium aids growth throughout the plant cycle, magnesium is needed for photosynthesis, and sulphur provides important minerals. 

foliage

liquid feeding

Liquid feeding is a popular way to provide nutrients to your plants by mixing nutrients into water, to create a nutrient solution. This can work for both soil growers and hydroponic growers and encourages healthy plant growth by socking the roots in nutrients.

If growing in soil, you should feed your plants the nutrient rich solution every other day to avoid over feeding. With soilless growing mediums, such as in hydroponics, you have complete control over which nutrients your plant will receive.

Avoid giving too many nutrients, if your plant is showing signs of nutrient lockout, act quickly. Nutrient lockout is when your plant is over fed and cannot take in any more nutrients or the pH level is not correct. Signs include the yellowing of leaves or your plant looking weak and flimsy.

Choosing a fertiliser can be confusing at first. Most will have the 3 main ingredients that your plant needs, that is, nitrogen, phosphorus, and potassium (also known as the NPK ratio). These will be shown as numbers on the fertiliser bottle.

In the vegetative stage the plant will need high levels of nitrogen, low phosphorus, and medium potassium (example, 9-4-5). In the flowering stage there will be less nitrogen, medium-high levels of phosphorus and high potassium (example, 3-8-7). Start by giving a low dose, gradually applying more until the plant is having maximum growth. 

Cannabis_Nutrient_Deficiency
Nutrient Deficiency, Be careful not to give too many nutrients - (CC BY-SA 3.0)

nutrients in hydroponics

Hydroponic systems such as the flood and drain, NFT and drop systems, allow you to have full control over the amount of nutrients your plant receives. If using one of these systems with water reservoir, you can choose between a circulating system and a non-circulating system.

A circulating system will allow any nutrient solution to fall back into the reservoir, before pumping it back up again. This will have some fresh nutrients, and some left over from the last feeding. With a non-circulating system, the excess water is drained off separately and a fresh nutrient solution is applied at every feeding. 

monitoring nutrient levels

It is important to monitor the pH and electrical conductivity (EC) to ensure your plants are receiving the nutrients at the correct level. If the pH level is too low, the solution will be too acidic and the micronutrients could increase, creating too high levels of nutrients.

If the pH level is too high, the solution will be too alkaline, the nutrients will decrease, and your plant may experience nutrient deficiency. Check your nutrient levels regulate using a pH and EC metre. A pH level of 5.5 to 6.5 is a good place to be.