Coffee grounds are included in this list of slow release fertilizers because they are now available free in quantities that can cover a lawn of at least 10,000 square feet or a quarter acre.
Try Lawn Fertilizer Experiment Using Coffee Grounds
I'm going to set aside about 400 square feet of my lawn for an experiment. I am going to forego applying any fertilizer to that plot. Instead, I will thinly spread used coffee grounds on the test area for the whole season, until the first serious snow.
As some of you know, I am a nut about mulching the lawn at least once a year with either chopped leaves or a combo of Canadian sphagnum peat moss and quality compost. The purpose of this layer of mulch is to give the earthworms and soil microbes the additional organic matter they need each year to supplement the food they manufacture on their own. Until recently, those were the only mulching options for a lawn that I could think of.
What happened was that last month Nancy and I started to get a 3-gallon plastic pail filled with used coffee grounds every few days. Our source is the new Pleasant Soul Café and Coffee Shop that has taken metropolitan Attica by storm. When Nancy suggested collecting the used coffee grounds for our garden, Angie, the head honcho, was enthusiastic. As well as offering the best food and coffee around, she wants her business to also be "green." So, on my test area I am going to maintain a thin layer ( 1/8 -inch to 1/4 -inch) of coffee grounds throughout the season. Then, in October, I will compare that area to the rest of my lawn, which will get its usual spring and fall application of slow-release fertilizer.
Coffee grounds are quite acidic with a pH between 3.5 and 5.0. That does not cause a problem, however, as long as you use a relatively thin layer of this material. Earthworms consider coffee grounds to be better than ice cream. One year of using coffee mulch will likely double my earthworm population under that test site. The coffee grounds alone offer 3 percent nitrogen to the soil, and when the earthworms chow down those coffee grounds, the outcome includes even more nitrogen, which is easily equal to the nitrogen in a regular application of fertilizer. I expect my test area to be greener, require less water, and need no additional regular fertilizer by the end of two years of mulching throughout the season with coffee grounds.
