Adjustable sensor on swathboard of mower

A mower configured to cut plant material as the mower moves over a field and deposits the cut plant material on the field, the mower including a header assembly having a cutter bed, conditioning rollers, and a swathboard, the swathboard being positionable to shape the cut plant material into windrows, wherein the cutter bed has a plurality of rotating rotary cutters, wherein said plurality of rotary cutters comprises at least one pair of oppositely rotating rotary cutters that sends a rearwardly-directed stream of cut plant material between the oppositely rotating pair of rotary cutters, wherein the header assembly comprises a sensor system mounted on the swathboard, the sensor system having a sensor configured to collect nutrient information of the plant material being cut by the mower, wherein the sensor is positioned on the swathboard to coincide with the location where the stream of cut plant material interacts with the swathboard, and wherein the sensor is moveable relative to the swathboard via a pivot tube co-aligned with a rockshaft on which the swathboard is mounted, such that the sensor pivots about the same axis as the swathboard.