Coffee Grounds

(as soil amendment)

Great source of nitrogen :: NPK 2.0 : 0.36 : 0.67

for Vermiculture

Worms love spent grounds, just be mindful that they are acidic and you don't want to drown your worms in them.

in Compost

Coffee grounds can be used as a good source of greens for Compost. As always, don't go too heavy on the nitrogen or it will smell.

as Mulch

You can apply spent grounds directly around nitrogen loving plants like tomatoes.

pH

A common belief is that coffee grounds as an amendment will acidify your soil. According to at least one study, however, this is untrue [1]:

"Less straightforward are the changes in pH that occur during decomposition. A commonly held assumption states that coffee grounds are acidic, but this does not hold true experimentally. While two studies on coffee ground composting reported mildly acidic pHs of 4.6 and 5.26, others have measured neutral (7.7) to somewhat alkaline (8.4) pH levels. One researcher found that the pH of soil treated with coffee compost increased after 14 to 21 days of incubation, gradually decreasing thereafter. Obviously the pH of decomposing coffee grounds is not stable and one shouldn’t assume that it will always, or ever, be acidic."