Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering


Four commercial-quality moisture meters were compared to the official air-oven method on 879 samples of corn from the 1979 and 1980 crop years. Samples ranged in moisture from 11% to 38%. Calibration biases and random variances were observed and quantified. Moisture meter performance characteristics were then related to typical pricing practices employed by Iowa country elevators;All four meters, Steinlite SS350, Burrows 700, Motomco 919, and Dickey-john GACII exhibited statistically significant calibration biases. The magnitude of calibration errors varied from approximately 1.5 points high to 3.5 points low, but was dependent on meter brand and moisture content. Regression equations developed from this study were used by meter manufacturers to recalibrate meters for the 1981 harvest;The coefficient of random variation for a meter test relative to an oven test on the same sample was found to be a function of moisture content. The smallest variability occurred at moistures between 15% and 20%. Meters became significantly more variable both above and below this range. Estimates of variability agreed well with similar estimates obtained by other researchers using laboratory apparatus;Random variations were identified with three sources; the oven test (contributing about 5% of total variance), the internal precision of the meter (contributing about 10% of total variance) and sample-to-sample variations in the corn (contributing about 85% of total variance);Both calibration bias and random variability can create inequities in corn pricing. Calibration biases are not precisely offset by the usual moisture discounting methods. Furthermore, the discount structure causes random variability to penalize the seller of corn more heavily than the buyer. A set of improved marketing practices is proposed to correct these deficiencies, and to distribute the effects of unavoidable errors more equitably among all traders of corn.



Digital Repository @ Iowa State University,

Copyright Owner

Charles R. Hurburgh, Jr.



Proquest ID


File Format


File Size

192 pages