CO₂ in Soil Easily Measured

Lucretia Sherrod is a biological science technician who believes that if the right lab equipment or procedure doesn’t exist, you just make it yourself.

Her latest creation is a modified carbon dioxide (CO₂) analyzer. With this, she and her colleagues have developed a rapid and cost-effective way to estimate carbon decomposition rates by monitoring soil respiration. Traditional methods of measuring CO₂ levels are labor intensive and time consuming.

Soil microbes decompose plant material and release carbon for possible storage in soil. But microbes also “breathe out” carbon as CO₂. The best scenario is when more carbon is stored in soil than is lost through microbial respiration.

Sherrod transformed a single-cell infrared gas analyzer meant for monitoring CO₂ levels in greenhouses into an easy and environmentally sound way to measure soil respiration. She can run 90 samples an hour, instead of 10 to 24 per hour using traditional techniques.

After a soil sample is incubated in a chamber for 3 days, Sherrod inserts a needle through the chamber’s seal and collects a sample of the atmosphere for analysis. Her system easily makes room for add-ons such as an oxygen analyzer.

Her test can measure the CO₂ produced and oxygen consumed when microorganisms eat soil organic matter. She has publicized this test with an abstract at the 2009 annual meeting of the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America. She is also writing a paper on the procedures. Any lab can easily build the test equipment for immediate use.—By Don Comis, Agricultural Research Service Information Staff.

Lucretia A. Sherrod is in the USDA-ARS Agricultural Systems Research Unit, 2150 Centre Ave., Fort Collins, CO 80526; (970) 492-7352.

"CO₂ in Soil Easily Measured" was published in the November/December 2010 issue of Agricultural Research magazine.