Observer Variability for Disk Meter Measurements of Forage Mass
- G.E. Aiken and
- D.I. Bransby
Inconsistency among research workers in estimating forage mass in grazing experiments would limit the value of forage mass estimates, but this problem has not been thoroughly examined. A study was conducted to determine variation among observers in using the disk meter to measure forage mass on tall fescue [Festuca arundinacea (L.) Schreb.] pastures which were grazed by steers (Bos taurus L.) at stocking rates of 2.0,4.5, and 6.0 animals ha−1. Four observers, with varying degrees of training and experience, were used to visually identify sites which represented mean disk meter height (DMH), determine DMH from random location of DMH measurements, and calibrate the disk meter for estimating forage mass. There was an observer-by-stocking-rate interaction for visual locations of sites considered to represent mean DMH. Slopes differed among observers for the regression of pasture DMH (estimated from randomly located sites) on stocking rate. Slopes for calibration equations also differed among observers. Results of this study indicate inconsistency among observers in using the disk meter to estimate forage mass, suggesting that caution should be taken when extrapolating forage masses from grazing experiments.
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