A Soil Probe for In-Situ Near Infrared Spectroscopic Measurement of Soil Carbon

76063S International initiatives are underway to reduce greenhouse gases in the air. The sequestration of carbon in agricultural soils is a candidate technology for achieving this reduction; however, more rapid and less expensive methods of measuring soil carbon are needed. This project will develop a soil probe for carbon measurement based on near infrared reflectance spectroscopy. The probe will measure carbon and bulk density in order to provide a rapid inventory of carbon on a field or project scale. In Phase I, a probe was designed that delivered low noise spectra during in situ field measurements in Kansas, Missouri, and Iowa. Calibrations using these spectra were used to measure soil carbon with a root-mean-square error of 0.5% or less. Phase II will automate the optical reference on the probe to make it practical for usage by a more general end-user. In addition, modifications will be made to the probe geometry to increase the accuracy of bulk density measurements. Finally, effective calibration methods will be identified, tested, and integrated into a user-friendly interface. Commercial Applications and Other Benefits as described by the awardee: The soil carbon measurements made by this probe should find use in auditting sequestered soil carbon, the subject of carbon trading and carbon offsets. In addition, the probe and calibration methods would be applicable to the measurement of other soil attributes that are important for making good agronomic decisions.