Method and device for non-invasively determining moisture content and uniformity of solid plant matter during on-line drying or cooling forced-air treatment featuring measuring primary operating parameters of temperature, humidity, and flow rate of forced-air entering and exiting the volume of solid plant matter moving through an on-line drying or cooling forced-air treatment device. Empirically determined data relating the influence of secondary operating parameters of volumetric bulk material transport rate of the solid plant matter, type of the solid plant matter, and physicochemical characteristics and properties of the solid plant matter, on the sensing and measuring of the primary forced-air operating parameters are used for process correcting raw temperature, humidity, and flow rate, parametric values of the forced-air entering and exiting the solid plant matter, leading to the determination of highly accurate and reproducible values of moisture content and uniformity of the solid plant matter. Moisture content and uniformity values correspond to the volume of the solid plant matter.