I have received a few questions from homeowners about using table sugar as a fertilizer substitute for their lawn. There have been a number of blog posts on popular forums that have repeated the idea and have popularized it recently. What’s more, there are even sugar-based products used in agricultural and turf systems that are marketed to increase crop yields or improve turf health.
Plants actually make their own glucose (a component of sugar) through photosynthesis when converting carbon dioxide and water into their own energy source. So why would adding sugar help plants?
Food for microbes
The idea behind adding sugar is that it is adding a food source for soil microorganisms. The soil microorganisms then consume this sugar (which is mostly carbon), and in the process, mineralize nitrogen or other nutrients making them plant available. These products are sometimes marketed as carbon food sources or stimulants.
These sugar-based products are more common in agricultural systems. Most often they are more complex sugars from products like molasses, and used as a liquid starter supplement or fertilizer at or near planting. There are some published reports in agricultural systems about molasses-type products resulting in a plant response through an increase in soil biological activity.
Your lawn may still need some fertilizer
In most cases, these sugars are consumed by microbes and used up within hours or days and they are not designed to replace the essential nutrients. The plants still need nitrogen, phosphorus or potassium, among other nutrients, for most of their needs, and sugar alone is not supplying these nutrients.
For more information about lawn fertilizers and practices, see Fertilizing lawns.