For a word we hear so often it's surprising how few people truly understand what "organic" means. Definitions differ between countries and their respective organizations, as does the scope of the term's usage (nutrients, pesticides, foodstuffs) but let's start with this fundamental concept:
Your garden is a living organism.
Organic gardening starts and finishes with the soil. Rather than importing nutrition in the form of mineral-based fertilizers (as is the case with hydroponics) the soil itself forms the primary cache of nourishment for your plants. Treat your soil to additional inputs. Create your own potting mixes. Brew your own compost tea! It's all part of being experimental and enthusiastic organic gardener!
It is often said that organic gardeners "feed the soil" rather than feed their plants directly. There is much implied here and the previous statement bears further consideration. Firstly, soil itself is undergoing a sort of composting process. In healthy soil, organic matter (such as fallen leaves, twigs, manure and other natural debris) is being constantly broken down by fungi and bacteria. These organic molecules are too large to be absorbed by plants-they only become available when the microbiology living in the soil has "processed" or "assimilated" them. This is a key distinction to understand. Hydroponic growing does not require the presence of microbiology in order to function whereas organic growing is wholly reliant on it.
Organic gardeners seek to work in tandem with natural processes. Rather than adding mineral-based fertilizers, they may use a top-dress of soluble humus or bat guano, perhaps applying some home-brewed compost tea-rich in beneficial microorganisms-to aid in the break down into ionic (or "plant-usable") form.
The diversity of life present in healthy soil is staggering, as is the complexity of the vast number of interconnected relationships that form the foundation of life on this planet. We are only just beginning to discover how these work.
Organic Growing Techniques Articles