An improvement in an apparatus for processing an agricultural crop, which processing apparatus has structure for separating waste from a crop to provide a clean yield product and an elevator for raising and delivering clean yield product to a point of use such as a bin, or the like. The improvement is a structure including an actuating arm for producing a signal indicative of a pressure being applied to the actuating arm. The signal producing structure is mounted to the crop processing apparatus so that the actuating arm intercepts clean yield product discharging from the elevator. This pressure value can be correlated with other data, i.e. combine width, elevator speed, forward speed of the crop processing apparatus, material density (lbs/bundle) to generate a flow rate value that can be continuously plotted to generate a yield map for a field.