Finished compost adds nitrogen, phosphorus, and potassium, making soil nutritionally rich. It acts as a pH buffer by bringing the pH to a neutral level (a middle ground between acidic and alkaline). Compost also saves you time and money since it dramatically increases soil’s water-holding capability. Water run-off is reduced, diseases are suppressed, and a healthy wildlife environment is created all thanks to compost.
The best way to get compost into your garden is to make it yourself at home. Lucky for us, the transformation of organic matter into this rich nutrient source is uncomplicated and inexpensive, and it doesn’t even smell.
Carbon and Nitrogen Sources - Guide to Home Composting