Compost

• Fresh grass clippings and green vegetation have a greater nitrogen content, and hence a lower C/N ratio, than wood chips or dried leaves. Recommended levels for C/N ratio at the start of composting is 30/1. At the end of composting, it should reach 10/1. If nitrogen levels are too low, the compost will not heat up. If they are too high, the compost microorganisms may be killed.
  
  

Agriculture

• During the early part of the 20th century, "sour soil" was the name for nitrogen deficiency in soil. The C/N ratio of soil is usually 10:1. If organic matter or fresh manure of C/N ratio of 30:1 is added to the soil, the soil microorganisms will tie up the available nitrogen and leave little or none for any crops. The nitrogen deficiency in crops such as corn or wheat shows up as yellowing leaves.
  
  

Marine Environment

• The C/N ratio from estuarine, coastal to open ocean areas ranges between 11 and 25. This indicates the lack of dissolved nutrients, nitrogen, in waters as they move from the land into deep seas. The nutrients are utilized by organisms in the photic zone, the area where light is available for photosynthesis, in shallow waters. The exception occurs in the high latitude southern ocean where winter darkness allows the movements of dissolved nutrients further towards deeper waters.
  
  

Human Bone

• The isotope C/N ratios in human bone provide an indication of a person's diet. Bone collagen originates from the protein content of the diet while bone carbonates and tooth enamel carbohydrate come from a combination of protein, carbohydrates and fats. Investigations of tooth chemistry from human remains in coastal Ecuador and Peru show that maize did not become a dietary staple until 1,000 BC, some 1,000 years after the first appearance of settled villages.