Biodynamics is the most advanced form of organic farming. It works with cycles of nature to grow grapes and make wine, and uses plants and animals to take the place of chemicals and fertilizers. You need to identify plants, bacteria and animals that live in a vineyard, and make them synergize with each other to form an environment that is completely unique. This creates farm individuality and distinction, on a piece of property, and translates that individuality into the wines.
Where does the flavor come from? Flavors are created in the vine. The building blocks are the minerals in the soil. If you keep applying synthetic chemicals, you are upsetting the minerals in the soil. So if you wish to express true terroir, you should be trying to keep the soil healthy. Let the minerals that are already there express themselves in the flavor in the vine.
Herbicides upset the balance of the vineyard simply because dead grasses are an essential part of the vineyard floor. Those dying grasses act as food for other species, and those act as food for yet another species. You go right down the food chain to the organisms that create the minerals for your plant to suck up and create the building blocks for the flavors. Your job is to create harmony in your land and in your grapevines, and in your wines.
Organic farming is not using synthetic chemicals. Biodynamic farming is doing that, plus going to the next level like making your own composts. In biodynamic farming, the strategy is not to feed the plant but to feed the soil. When you feed the soil the plant can feed when it wants. That way you get a more balanced growth, and the vines are much stronger and have a higher disease resistance.