Soil organic matter sensing with an on-the-go optical sensor

► Optical sensor with 660 and 940 nm LEDs to measure soil organic matter content (OM). ► Sensor evaluated with soils in the lab, reflectance and OM had R2 of 0.91. ► Field tests showed ratio of prediction to deviation as high as 3.56 and R2 of 0.91. ► Sensor comparable with NIR spectrophotometer for OM mapping pattern with R2 of 0.86.