As a foliar application:
Molasses is a fairly versatile product, it can serve as a plant food as well as a an additive to improve a fertilizer mix or tea. Dry molasses can be used as an ingredient in a fertilizer mix, and liquid molasses can be used alone or as a component in both sprays and soil drenches.
Most people tend to use Blackstrap Molasses, but feed grade molasses will work great and is much more affordable.
Molasses is a great source of carbohydrates that stimulates the growth of beneficial microorganisms. “Carbohydrate” is really just a fancy word for sugar, and molasses is the best sugar for horticultural use.
Molasses is a great source of trace minerals.
In addition to sugars, molasses contains significant amounts of potash, sulfur, and a variety of micronutrients. Because molasses is derived from plants, and because the manufacturing processes that create it remove mostly sugars, the majority of the mineral nutrients that were contained in the original sugar cane or sugar beet are still present in molasses. This is a critical factor because a balanced supply of mineral nutrients is essential for those beneficial microbes to survive and thrive. That’s one of the secrets we’ve discovered to really successful organic gardening, the micronutrients found in organic amendments like molasses, kelp, and alfalfa were all derived from other plant sources and are quickly and easily available to our soil and plants. This is especially important for the soil microbes, including bacteria that depend on tiny amounts of those trace minerals as catalysts to make the enzymes that create biochemical transformations.
These microbes and beneficial bacteria break down organic fertilizers and “feed” it to our plants.
One final benefit molasses can provide to your garden is its ability to work as a chelating agent. This really means that it binds to the molecules in a form that’s easily available for microbes and plants. Chelated minerals can be absorbed directly and remain available and stable in the soil.
As a soil amendment:
Dry molasses is actually a ground grain waste “carrier” which has been coated with molasses. This gives dry molasses a semi-granular texture that can be mixed into the soil. This is intended to get the same benefits as the liquid, but at the root level.
Molasses is a good, quick source of energy for the various forms of microbes and soil life in a compost pile or good living soil.
Molasses is used in teas to feed the microbes and bacteria, it is essential for the bacteria, without a food source they will not reproduce and grow
*I usually use tea in my compost tea, early in the season I may drench the soil in the root zone with Molasses, Kelp, and Fish.
The normal amount used to drench the soil can range anywhere from 2 oz per gallon to 8 oz depending on what yours goals are.
The amount used in tea depends on your individual recipe and how much you intend to brew.
I use 5 cups per 55 gallons.