Nondestructive Single-seed Moisture Determination in Soybeans by RF Impedance Measurements

Abstract

Impedance measurements were taken at frequencies of 1 and 5 MHz on a small parallel-plate capacitor holding single soybean seeds between and in contact with the plates on samples from two cultivars each from soybean producing areas in the Midwest and the Southeast. Moisture contents ranged from 7 to 20%, wet basis. Calibration equations were developed from these measurements and oven moisture determinations on individual soybeans. Two calibration equations are presented, one with a single variable involving only capacitance measurements at the two frequencies, and another with three variables including capacitance differences and complex admittance differences. The two equations performed comparably in these tests with standard errors of 0.5 to 0.6% moisture content. Thus, the technique can provide rapid nondestructive tests for moisture content of single soybeans and offers promise for practical use.