Farming practices without chemical fertilsers and other synthetic substances are classed as organic. Historically, chemicals such as urea and DDT were brought into farming in large scele towards the later part of 20th century - previous to this, farmers didn't have the knowledge and simply put, were happy enough with things as they were; as most of us today would be. After all, home grown food is often the nicest, most tasty food we put on our plates.
For some reason, during the 1960's and 1970's the concept of organic food became a separate entity to the normal food we were then buying. Consumers had been effectively duped into believing that what they were buying, was food as nature intended, it not appreciating that the chemicals which were added during growth of the 'normal stuff' were what actually made the food abnormal in the first place.
Rachel Carson, a prominent writer, biologist and ecologist established public awareness of these issues via Silent Spring, a book she wrote which basically brought about major controversy on the use of agricultural chemicals and synthetic pesticides in particular. As a direct result of this book, and the growing concern over the use of farm chemicals which consumers were suddenly more aware of, chemical regulation procedures were put into place, and when the demand for organically grown food rose, so did the need for further regulatory procedures to cut down on the ecologically destructive and toxic chemicals.
Today, organic food is finally reaching an all time high of acceptance from consumers, so its demand is increasing - more 'organically acceptable' agricultural procedures are gaining momentum, and it seems even though it is more expensive than chemically treated foodstuffs, it is healthier, and it is that health factor which is winning the battle against chemically treated consumables.
A creation of a whole new set of ideas about organic standards which first came into debate in 1990, took over ten years to refine to relative perfection, and they will still evolve as new practices come into force. It is by these standards now that, organic food and other products such as wool in the USA is grown/gathered.
All of this though begs the questions - why can't farmers just grow food without chemicals at all, why does it need regulation, and why were chemicals introduced into grown food and other consumables in the first place; I think you already know the answer though, and that's money.
In this modern technological age where farmers are in direct competition between each other to gain the bigger contracts of the supermarkets and other food retailers, they have to be cheap. They simply can't grow the vegetables (for example) as fast as the grocery store can sell them, so they have to resort to other methods to keep up, or did do at least until the consumers voice began to ring out strong and true.
Organic food is no longer a small niche in the food desires of Americans; it is becoming what everyone wants. Everyone now wants and feels the need to eat in a more healthy fashion with the onset of so many new medical conditions which prove costly as it is; a little more expense to eat something grown without strong use of chemicals (which could 'theoretically' make it worse) might mean a saving health-wise instead.
The organic food trend of today is growing ever-stronger, and not just for vegetables even though at one point organic purchases totalled over 40% of all organic buys. Meat and fish which is organically produced is still at the lowest of all food purchases, but is moving up the chain too. Dairy, bread and grain, beverages and snacks are all becoming more and more popular.
Today there are more Organic supermarkets popping up everywhere, sometimes in certain areas more than others - almost as though people in one state are more 'organic' than others but on the whole it is more of a blanket change than just a few people trying to eat in a healthier way, the amount of people eating organically is far more substantial than most realize. Suddenly people have more choice, and this is obviously because the demand is there. The world is finally going organic, and with any luck the bigger grocery store chains will have to meet this demand, rather than flood the market with low-cost chemically treated alternatives.