Compost Materials C:N Ratios

When gathering materials for your compost keep in mind the ratio of carbon (C) to nitrogen (N). The best ratio is between 25 to 30 parts carbon to 1 part nitrogen, or 30:1. This means most of the materials in your compost should be carbon. If the C/N ratio is higher than 30 the pile will take a long time to decompose. If there are too many materials high in nitrogen the compost will likely begin to release a smelly ammonia gas. The C/N ratio does not need to be exact, add about 2 to 3 pounds of nitrogen materials for every 100 pounds of carbon materials. High carbon materials like sawdust will require more nitrogen materials to ensure good decomposition. Use the flash cards below to test your knowledge of material C/N ratios.