A multi-sensor system rapidly measures diffuse reflectance of soil, soil conductivity, and other soil properties in situ, in three dimensions. The system includes a tractor-drawn implement containing a sensor shank used for X-Y axis measurements, a hydraulic probe implement containing a sensor probe for −Z axis measurements, and a set of visible and near-infrared spectrometers, controls, and firmware that are shared by each implement. Both implements include optical sensors and soil electrical conductivity sensors. The probe implement incorporates a sensor that measures insertion force, and the shank implement includes a soil temperature sensor. These combinations of sensors are used to calibrate the system and to characterize the soil properties within a field or area. Geo-referenced soil measurements are collected with the shank implement to identify optimal locations for conducting sensor probe insertions. The probe implement is then used for sensor probing and for collecting soil core samples for lab analysis.