Using coffee grounds as a compost soil amendment is environmentally and economically friendly, and it is advantageous for your garden plants. Coffee grounds lend essential minerals and nutrients, including phosphorus, potassium, calcium, magnesium, nitrogen, sulphur and copper. Adding coffee grounds is as easy as incorporating a commercial chemical aid, and it is something you (perhaps) already have inside your home. Coffee grounds can be tilled into the soil, applied directly on top, or diluted with water and sprayed as a liquid fertiliser.
Collect your coffee grounds. You will need a considerable amount of coffee grounds, so if you will be using your own coffee byproduct, begin its collection at least a month prior to your gardening date. To help you remember to save the used grounds, place an empty coffee can, bowl or bucket next to your coffee maker for easy collection. You can store a week's worth of grounds inside, and then transfer to an outside bucket. If you are not a coffee drinker, or wish to begin the fertilising immediately, visit a local coffee shop and ask for some used grounds for compost purposes. Starbucks, for example, gives away coffee grounds as part of a corporate environmental program.
Till the grounds into your soil. Till enough coffee grounds to reach 25 to 35 per cent of mineral soil volume (that is, aim for a 1:4 coffee-to-soil ratio). Coffee grounds can also be placed directly on top of the soil; the nutrient effects will still benefit the plant and soil. To maintain a healthy soil Ph level, consider mixing dried leaves, dead grass or mulch with the coffee grounds before sprinkling on top of the soil. Due to the acidity, topical application of coffee grounds also aids in warding off garden pests and diseases. The use of coffee grounds in or on the soil will have an immediate benefit (nitrogen release) as well as a long-term benefit of supplementing and stabilising the soil.
Dilute coffee grounds with water in a fertiliser spray bottle and spray the soil as you would if using a commercially purchased liquid fertiliser. This is particularly useful for indoor plants, and leaves a nice bistro-smell as opposed to chemical spray.
Mix coffee grounds with compost or in worm bin soil to create homemade fertiliser. You can add coffee grounds to your compost pile or worm bins to create a nutrient-rich fertiliser that can then be added to your garden soil. Coffee grounds are high in nitrogen, which means they will generate heat in the pile and allow for faster composting. When adding grounds to compost, take care to not overpower the mix; use a 25 per cent volume ratio. Coffee grounds are very acidic; to counterbalance this acidity in your compost pile, consider adding 1 or 2 teaspoons of lime to the pile.