In one embodiment, a method implemented in an agricultural machine harvesting alfalfa plants, the method comprising: receiving, in real time, input corresponding to a plurality of sensed parameters corresponding to alfalfa plant height and cut alfalfa volume; associating the cut alfalfa volume to an alfalfa stem diameter; and automatically determining a feed quality value for the alfalfa plants based on the sensed alfalfa plant height and the alfalfa stem diameter.