Why do I need a special type of fertilizer to grow cannabis, aren't they just weeds in the wild? Why can't they grow in regular dirt?
While cannabis plants will grow in a lot of conditions, as a farmer, you are looking to optimize the size, weight, density, potency and overall quality of your buds. In order to do that, you will need to fertilize your cannabis plants in such a way that they can produce at their best.
Yes, you can plant weed seeds in dirt and possibly grow a plant without any fertilizers or special nutrients. But chances are that you don't happen to live in a place with very rich, fertilized soil that carries just the right blend of nutrients needed by a marijuana plant to thrive.
Cannabis plants which don't get the right levels they need, especially in the flowering/budding phase, tend to grow small and airy buds. In extremely poor conditions, some cannabis plants may just sprout a few white hairs (pistils), and never actually form any real buds at all.
Because of that, I encourage growers to learn about the type of nutrients and special fertilizers needed by a cannabis plant, and at least start with good soil before you get started growing if you're determined not to use any nutrients.
And if you are determined to grow organically with no added nutrients, I encourage you to learn about how you can actually compost your own organic super soil in such a way that you actually don't ever need to add any extra nutrients at all.