NONDESTRUCTIVE SINGLE-SEED MOISTURE DETERMINATION IN SOYBEANS BY RF IMPEDANCE MEASUREMENTS

Impedance measurements were taken at frequencies of 1 and 5 MHz on a s mall parallel-plate capacitor holding single soybean seeds between and in contact with the plates on samples from two cultivars each from so ybean producing areas in the Midwest and the Southeast. Moisture conte nts ranged from 7 to 20%, wet basis. Calibration equations were develo ped from these measurements and oven moisture determinations on indivi dual soybeans. Two calibration equations are presented, one with a sin gle variable involving only capacitance measurements at the two freque ncies, and another with three variables including capacitance differen ces and complex admittance differences. The two equations performed co mparably in these tests with standard errors of 0.5 to 0.6% moisture c ontent. Thus, the technique can provide rapid nondestructive tests for moisture content of single soybeans and offers promise for practical use.