Do You Take Sugar With Your Dirt?


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? 


  1. Hey, if my doctor won’t let me have those carbs and sugars anymore, do you think I’m going to let my garden and compost pile have some, while I’m denied? Seriously, as noted, there isn’t a lot of hard science behind this, but who knows? Might be worth a try and would be a good way to get rid of that molasses that is sitting in that bottle stuck to the pantry shelf.

  2. I would be a little careful about adding too much carbon (in the form of sugar) to your compost or dirt because the microbs that eat the carbon also need nitrogen which they will take from your soil, making it temporarily unavailable to your plants. I am a plant biologist and study invasive plant issues here in Nevada. Adding sugar in a widely accepted method of reducing available nitrogen in the soil. Sorry if that is all a little geeky but the bottom line is more sugar equals less nitrogen for your plants.


  3. It all makes sense. Sugars are the catalyst for fermentation in our alcoholic beverages so using them to grow bacterias isn’t as outrageous as it seems.

    Great post Amy.

    PS. Organic gardening is an ART not a SCIENCE.

  4. Oh, please, Stuart! And what’s wrong with science? First science must endure the attacks of the irrational in the name of faith and now we have to draw lines between science and art?

    To quote my dictionary, science is “the systematic study of the structure and behavior of the physical and natural world through observation and experiment.” Any gardener who is so incurious as not to observe and study the garden he tends deserves to be left sitting in the dark of his cave endlessly discussing questions without discovering answers.

    I’d rather hang with the group who is here to compare observations and add to our stock of knowledge along the way.

    Let’s experiment!

  5. Hey, I’m with Sinclair. What’s wrong with science? When you get right down to it, science is art (ever seen electron micrographs of fungi?)…and as a microbiologist, adding sugar just boosts your microbial numbers, at least temporarily (at the expensive of other nutrients, such as nitrogen like Wendy mentioned above) – but eventually it’ll just level out, so I don’t think adding it to your compost pile to give it a ‘boost’ would be anything but a temporary fix. It’d be better to use the molasses to make gingerbread cookies, then add the cookies you don’t eat (like that would ever happen) to the pile – then you get some other stuff too…

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