First, what makes up brewed coffee, besides caffeine? Nutrition experts agree that coffee grounds contain magnesium, phosphorus, potassium, copper, manganese and trace amounts of calcium. Nitrogen, phosphorus and potassium are the ingredients necessary for garden soil. They coincide with the figures you see on most fertilizer bags. So coffee does have what plants need to grow.
There seems to be some debate about whether or not coffee produces nitrogen. Most agree that coffee grounds contain 1.5 to 2.2% nitrogen. However, some feel that the nitrogen is not available to the soil or the plants until the grounds themselves begin to decompose.
Others say you must compost the coffee grounds with other plants to release the nitrogen in the decomposition process. They recommend adding nitrogen to the soil if using only the grounds. The rotting grounds attract nitrogen-consuming microbes, thus, the need to add nitrogen if using only coffee grounds as a fertilizer.
So to be on the safe side where fertilizing is concerned, you may be better off tossing your coffee grounds along with other compost into the garden in the fall and winter to allow them time to be of best use for spring planting. Continue reading “Do Old Coffee Grounds Work As Fertilizer?”