When growing organically the best technique to use is to make a soil mix that is completely organic and contains all the necessary nutrients for the duration of your grow.
Generally, the easiest to is to start with a soil mix that has some organic elements in it already. Something like Sunshine Mix or Pro Mix, both are commonly available at places like Home Depot if there are no grow shops in the neighborhood.
Next, you want to add something that will allow air to flow into the soil, commonly Pearlite is used, but you could also add rice hulls or pumice, which is very textured and quite porous, making it a great soil additive. Depending on your starting soil it might already have some permit in it so double check or you will end up with too much. It should be in about one-to-10 ratio. Next double check that there is Dolomite lime mixed in, as it will bring the PH of the soil down to 5.0-7.0, which is the ideal spectrum for cannabis plants.
The next thing to add would be a mycorrhizae mixture, there are several on the market. This is a beneficial fungus that really helps with developing root systems, this was mentioned in depth in my root zone article.
Two other great products to use are fulvic and humic acid. There was a major study done at Ohio State University which proved that Humic acids increased plant growth. These acids are created by soil-based micro-organisms and assist the plant in the assimilation of minerals and nutrients. Fulvic acid also is closely related to enzymes, helping to increase their availability in your soil.
The next thing to add is some bone meal and guano. For a regular-sized bag of mix, the best ratio is eight cups of the bone meal and two cups of a guano. Both are good sources of phosphorus. If you are growing a kush or a sativa you should also add one cup of Epsom salts to increase the magnesium in the soil.
One key aspect to making your own soil — and a great tip for the environment — is to compost. Composting can be very easy and will also help you get rid of unwanted leaves and stems from previous grows. To start with, buy a compost bin and start layering your organic waste into it. Between the layers it is advisable to add one cup of dolomite. Mix it into your soil using a one-to-10 ratio.
The final and best step is now all you have to do is water your plants with PH balanced water as they will take in the nutrients over the course of the growth cycle. You could always supplement an organic tea with a higher percentage of P (phosphorous) and K (Potassium) during the middle of flowering.
Keep on growing!