Utah State University Extension
Time the number of seconds required to spray the measured calibration plot. It is important to be as consistent as possible with the speed of the tractor (gear, range, rpm’s). Calibration should take place on the same type of terrain that will be sprayed.
Whitesides, Ralph, "Simple No-Math Calibration of a Vegetable Boom Sprayer" (2014). All Current Publications. Paper 1077.