comparison of coefficient of variation with non-uniformity coefficient in evaluation of grain drills

external fluted feed rolls are commonly used in grain drills. the fluted feed roll meters a volume of seeds and does not singulate the seeds as do the precision planters; therefore, there will be inherent variation in the number of seeds delivered per unit of time. this research was conducted to investigate the effect of seed meter drive shaft and ground speeds and outlet positions in a grain drill on the variation in wheat seeding rate and seed flow evenness from various outlets in short time intervals using the coefficient of variation (cv) and the non-uniformity coefficient (nuc). in this study, a grain drill with straight fluted metering mechanisms was evaluated on a test rig. two rotational speeds of 16 and 23 rpm and two speeds of 2.5 and 3.6 km h-1were selected for the seed meter drive shaft and the movement of the test rig, respectively. the results showed that, for a given test rig speed, the seeding rate changed proportional to the seed meter drive shaft speed, whereas for a constant speed of seed meter drive shaft, the seeding rate decreased as the speed of the test rig increased. also, the seeding rates from all outlets were not the same. outputs of some of the outlets were autocorrelated, for which selecting 12 or 24 seed samples randomly out of 36 consecutive samples were not essentially non-autocorrelated. increasing rotational speed of seed meter drive shaft significantly increased the coefficient of uniformity of all outlets. the seed breakage was significantly increased with the speed of seed meter drive shaft. the cv and nuc exhibited similar trends. it can, therefore, be concluded that in grain drill evaluation, either cv or nuc could be used as an index of seed flow non-uniformity.