Total organic carbon is a measure of recent and historic organic additions to soil, in most cases from either native vegetation or agricultural crops and pastures. Other sources of soil organic carbon can be from compost, manure or mulch applications. Turnover rates for different types of soil organic carbon can vary from one month to thousands of years depending on composition.
Measuring total organic carbon provides information related to physical and chemical aspects of soil and overall soil fertility. Total organic carbon influences many soil characteristics including colour, nutrient holding capacity (cation and anion exchange capacity), nutrient turnover and stability, which in turn influence water relations, aeration and workability. Heavier textured soils (loams and clays) have a larger capacity to retain and store carbon through the physical protection of organic matter and soil fauna.