Many people drink a pot or two of coffee per day. If you throw your coffee filters and grounds down the sink or in the garbage, they serve no purpose. Coffee grounds, as ground up coffee beans, offer good organic soil nutrients for vegetable gardeners and are especially good for green leafy vegetables.
History & Composition
Establishing the history of the use of coffee grounds in gardening is very difficult. As with many folk-practices, early uses of coffee grounds were likely home experiments that worked well enough to warrant further academic study. Once the use of coffee grounds in vegetable gardens began being studied, coffee grounds were shown to have 1.45 percent nitrogen and to contain calcium, magnesium and other trace minerals not often found in other organic fertilizers, according to Cheap Vegetable Gardener.
One easy way to use your coffee grounds is to add them to your compost pile. If you use paper filters, the filters are also good compost material. Coffee works well in either traditional compost piles where you manually turn the material periodically, compost bins where you rotate the bin to turn the material, or worm composting, where the worms convert the material to organic wastes and worm casings. Adding compost to your vegetable garden will help your vegetable plants survive stress, according to the University of Florida.
You can add a small amount of coffee grounds directly to your vegetable garden's soil before an expected rain or before watering your gardens. By adding a tablespoon or two to each plant, you are effectively adding a slow release nitrogen fertilizer. If you want to make a gentle, but fast acting, liquid fertilizer, add the equivalent of a ½ pound coffee can of coffee grounds to 5 gallons of water and let it sit for 24 hours. Strain the solids and water your vegetables with the liquid. Applying coffee based fertilizers to your vegetable garden will help increase nitrogen levels and offer trace nutrients to your vegetable plants not available from other sources.
Coffee grounds applied to the surface of the soil serves both as a fertilizer and as mulch that can help the soil retain water. If using coffee grounds as mulch, put at least a full inch of grounds down. Coffee grounds can cake badly, making thinner mulches less effective at retaining water. Using coffee grounds as a mulch can help keep your vegetable plants more hydrated during the heat of the day. In addition, as coffee ground mulch breaks down, it adds nitrogen to your soil, which will help to fertilize your vegetable garden.
Some people claim that coffee grounds are acidic and will make your soil acidic. However, as long as you are using used coffee grounds, most of the acid is removed during brewing. The average pH of coffee grounds is 6.9, but that may vary, depending on your brewing method and the type of coffee brewed, according to Cheap Vegetable Gardener. If your coffee grounds are too acidic, adding them to parts of your vegetable garden may, according to Louisiana State University, affect the mineral content of the soils and may harm the ability of your vegetables to take up micronutrients and minerals from the soil.