First experiments on ultrasonic crop density measurement

An on-line crop density measurement delivers interesting information about the local crop condition. Once this measurement is established in a non-destructive way, crop density monitoring could be performed during the growing season and results would immediately be used for a site-specific application of nitrogen. s work, some primary results are shown from an ultrasonic crop density measurement. A commercial sensor, normally used for level measurements, is equipped with an extra output, providing a signal corresponding with the ultrasonic wave transmitted through a band of crop. Because of the properties of the measured signal, a non-linear transformation of the measured signal is necessary. With the result of this static compensation, a good estimation can be found of the energy in the received wave, closely related with the volumetric density of the crop. he appropriate signal is found, an experimental set-up is constructed for dynamic crop density measurements. A small wagon is placed on two parallel rails with a stroke of crop in between. On both sides of this wagon, two ultrasonic transducers are placed. One as transmitter of the ultrasonic wave, the other one as receiver at the other side of the crop. With this arrangement, a first calibration curve is made, delivering an exponential relationship between the transmitted energy and volumetric crop density.