by Greg Green
The three major nutrients that are found in soil are Nitrogen, Phosphorous and Potassium or NPK for short. NPK can come in two forms – with the soil or as a stand-alone fertilizer (usually in a bottle). When you look at the bag you will see that the % of each part is stated. Such as 20:20:20. This means 20% N, 20% P, 20% K. The remaining 40% is just other elements that make-up the soil. In liquid it would usually be water. This ratio can change between different types of nutrient and soil brands so we need to understand what Cannabis likes.
Cannabis plants like good levels of N and a normal level of P and K during vegetative growth. You need to pick a bag that has all three, not just 10:20:0. When looking at chemical fertilizers you need a mixture that has the first number higher or equal to the rest. 12-12-12 is fine, 20-20-20 is fine, 12-6-6 is fine and 18-4-5 is fine. The 12-12-12 and 20-20-20 are the best ones to find. Something like 8-20-20 is not suitable for vegetative growth. Bags with higher P are for flowering plants. As a grower we do not transplant to new soil for flowering. We simply use plant feeds to bring up the P levels during flowering.