Increasing soil carbon will increase total soil organic matter (SOM), which is the very foundation for healthy and productive soils (1). Organic farmers often judge and monitor soil health based on the amount of organic matter in each farm field. Active soil organic matter refers to a diverse mix of living and dead organic materials near the soil surface that turn over or recycle every one to two years. Active organic matter serves as a biological pool of the major plant nutrients. The balance between the decay and renewal processes in this biological pool is very complex and sensitive. The populations of microorganisms that make up the biological pool are the driving forces in soil nutrient dynamics. Together they also play a key role in building a soil structure that both retains and freely exchanges nutrients and water—a soil where plant roots thrive (2). Maintaining the concentration of SOM above a threshold level is essential for maintaining soil health, productivity, and sustainability. Loss of SOM leads to degradation of soil structure, reduction in soil water-holding capacity, and exacerbates climatic extremes. Thus, judicious management of the soil carbon pool is necessary (1).

1) Magdoff, F and Van ES, H, Building Soils for Better Crops, Sustainable Soil Management, SARE Outreach Publications, Brentwood, Md, 2009.
2) Keith R. Baldwin, Crop Rotations on Organic Farms, North Carolina Cooperative Extension Service (2006), www.cefs.ncsu.edu.