"Dear Sir, I know you highly recommend putting sugar on my lawn to feed it and control weeds, but how much? How should I apply it?"
Since I had responded to every other sugar related question with a comment along the lines of:
"Um no. Putting sugar on your lawn would be like sprinkling corn chips into Lake Michigan. I just cannot think of a good reason to do it. It won't hurt anything, but neither will licking the inside of your elbow. I assume you don't do that, do you?"
The elbow lickers are a persistent bunch. The questions just kept coming unabated. Keep in mind, ALL my previous answers were prominently posted with outspoken tags like "Don't put sugar on your lawn!"
I've tried to do the research on this, but from everything I can find there's absolutely nothing to back up the claims made about sugar as a great lawn additive. Let me share some of the hypotheses that have been put out there under the guise of science.
Hypothesis 1) Sugar enriches the soil by feeding the microbes. Active microbes = good soil.
Reality Check) Yes, active microbes = healthy soil, but this only holds true when the microbes are actively feeding on real organic matter. Sugar may provide a brief burst of activity for those microbes that are capable of feeding on it. Once the sugar is gone though, the microbes will return to a natural level based on available organic matter sources. Since the soil is enriched by the nutrients given off during the decomposition of organic matter, the sugar does nothing more than get the microbes briefly active by feeding them a food source that has no long term benefit.
Hypothesis 2) Sugar suppresses weeds by creating healthier soils. Weeds opportunistically take over unhealthy soil, so the healthier the soil is, the more it will encourage grass growth over weeds.
Reality check) Weeds are plants, just like your grass. They grow when the soil is good. Certain types of weeds can tolerate poor quality soil, but they'll still do better in good soil. Enriching the soil in any way shape or form will benefit all the existing plants. The argument is moot anyway since we have already shown that sugar doesn't actually do anything to enrich the soil.
When someone is promoting a product or service, it's up to them to prove that it is of value. "What have you got to lose?" doesn't cut it. They need to show reasonable studies performed by impartial professionals. A hypothesis is simply a conjecture until sufficient proof has been gathered to promote it to the level of theory (aka: accepted explanation). "Sugar will improve your lawn" is a hypothesis that has gathered no such evidence. Whether the idea is based on sound scientific principles or not is actually irrelevant. It needs to stand up to testing.
Want to try testing the theory yourself? Go for it! Sounds like a fun science project if you have a middle school child at home. Just make sure the test is blinded. Get a bag of topsoil and a bag of grass seed. Weigh out and put the exact same amount of soil and grass seed into two separate pots. Label them A & B. Add sugar to one of the two, and continually add an identical amount of water to each while keeping the two pots in the exact same area, so they get the same amount of sunlight, same air temperature, etc.
Finally, at intervals of two weeks ask a few impartial observers to analyzed the two pots and make judgements on color, height, feel, etc. It's very important that none of those observers knows which pot was treated with sugar and which wasn't. This way, they won't be biased in either direction, no matter how subconsciously. Write down their comments and analyze. If in fact you DO do this, please let me know how it goes. I'll even post pictures if you send them.
I love the concept of non-toxic, homespun remedies for your lawn and garden. I do not love the concept of wasting time and money just so that I can feel good about having not used chemicals.