Molasses is broken down by the bacteria in the soil into forms that the plant can use, primarily nitrogen, potash and various micronutrients. Molasses is a good source of carbon for the bacteria in the soil, so it can help the number of bacteria multiply. If you are growing all organically, I can see the benefit of diluting molasses in water and applying it during watering. If you are supplementing your soil with a chemical fertilizer that contains the necessary micronutrients, then molasses really won't do anything to help you out, but it won't hurt either.