This publication discusses how soil organic carbon has a wide range of crucial roles in agriculture. It impacts crop productivity, soil health, the movement of water, and removal of contaminants. Key themes of this publication include how soil organic carbon is closely related to soil organic matter, but the two are measured differently; soil organic carbon is linked to many aspects of soil health such as nutrient exchange, soil water holding capacity, and it provides great value on the farm; carbon markets are focused on changes in soil organic carbon stock that result from the application of new agricultural management practices; and the stock of soil organic carbon in a field is based on organic carbon concentration, depth of sampling, area of the field, and adjustments for other soil characteristics.