Determining Moisture Content of Hay and Forages using Multiple Frequency Parallel Plate Capacitors

This study was conducted to explore the use of dielectric impedance measurements at multiple frequencies, to predict the moisture content of hay and forages of unknown density, material volume, and material composition on a static test stand.The impedance measurements were found to be relatively successful in predicting the moisture content of legumes (alfalfa, clover) and to a lesser extent grasses (brome, orchard) and one grass/legume mixture (brome/clover). The measurements were less successful in the prediction of moisture content of a second grass/legume mixture (brome/alfalfa). The coefficient of determination (R 2 ) between the predicted and actual moisture contents were 0.95, 0.91 for alfalfa and clover respectively; 0.74, 0.78 for brome and orchard grass; and 0.94, 0.65 for alfalfa/brome and clover/brome mixtures. The frequencies used in the prediction equations were in the 900 kHz to 13 MHz range with the exception of 5 Hz frequency used in the clover prediction equation. The moisture content prediction capability was not affect by the density or the amount of material in the sensor. However the sensor required separate calibration for each crop