Well, maybe. Texas organic garden guru Howard Garrett uses it in the soil, in compost piles, and in all kinds of teas and potions. The idea is that the sugars give beneficial bacteria something to eat, and once you’ve built up their population, they’ll go searching around the garden for other munchies, including organic matter that, with their help, can be broken down into forms that are easier for plants to use. According to an article on Rodale’s New Farm website, Garrett said,
"Everyone has used molasses, by itself or with tea, but we are now using dry molasses, as fertilizer, and having dramatic results," he said. Applied at 800 pounds per acre, dry molasses provides a natural food source for indigenous microbial populations in the soil. It has another benefit, particularly in Texas — fire ants don’t like it.
There’s not a lot of hard science on this (welcome to organic gardening, folks), but the USDA was kind enough to study the effects of molasses on the growth of human pathogens like E. coli and Salmonella in compost teas. Sure enough, if you take manure–even manure that’s been well-aged and heated so that the little critters are at undetectable levels–and you feed them some sugar, they multiply and prosper. Bummer.
What else do we know? A report from the Hawaii Agricultural Research Center showed that molasses reduced populations of harmful nematodes and generally improved plant health. A story from the Australian Organic Journal looked at the impact of several popular soil amendments, including molasses, kelp meal, fish emulsion, and others, and did find some increase in populations of soil-dwelling microbes, but found that the results varied widely depending on how much you applied. (Lower application rates might actually be better.)
Feed stores sell dry molasses, and, well, you know where to get the liquid stuff. So tell the truth– do you serve your dirt dessert?