The Cannabis Grow Bible
by Greg Green
Feeding is the process of adding to your soil what the plant has taken out. You will only need 3 types of feeding solutions throughout your plants growth. You will need a bottle of feed where the NPK has equal or higher levels of N than P and K and you will also need a bottle that has higher levels of P than N and K. The first one is to be used during vegetative growth and the second is for flowering. You will also need a third bottle of secondary nutrients.
You should only feed your plants when they need it. The amount of feeds that you will use is relative to your growing conditions and strain. Most plants only need to be feed every fortnight at 50% or less than what it says on the label. Marijuana plants burn easily. So never mix your solution at 100%. If it says use 1 cap full of feed per 3 gallons of water, then use 1 cap full per 6 gallons of water. Sometimes you might even end up burning them using these low levels. This goes for both flowering, secondary nutrients and veg feeds. You should never have to feed cannabis plants once a day. During flowering simply switch the feeding bottle over to the one with the NPK where P has higher levels than N and K. You may want to add secondary nutrients once every 3 weeks to your grow. Epsom salts is a great way of giving your plant Mg, which is probably the most important secondary nutrient.