SOIL ORGANIC-MATTER, CEC, AND MOISTURE SENSING WITH A PORTABLE NIR SPECTROPHOTOMETER

Soil reflectance data were collected with a portable near infrared (NI R) spectrophotometer and were correlated with soil organic matter cont ent in laboratory and field tests. Laboratory calibrations yielded an r(2) of 0.89 and a standard error of prediction of 0.40% organic matte r with 30 representative Illinois soils at 1.5 MPa and 0.033 MPa moist ure tension levels. Limited in-furrow field operation produced much hi gher errors, due to the movement of soil past the sensor during data a cquisition. Estimation of cation exchange capacity (CEC) and soil mois ture content was also accomplished in the laboratory.