EFFECT OF INSTRUMENT PARAMETERS ON THE ACCURACY OF BULK SOIL ELECTRICAL-CONDUCTIVITY MEASUREMENT

The apparent heterogeneity of bulk soil electrical conductivity (ECa) resulting from field determination using potentiometric measurement is affected by the design of the instrument that measures the soil property. This scaling (Cushman 1986) of the analytical instrument is dependent on soil and experimental conditions like dispersivity, salt distribution, and distance from the application point of the saline solution. We present an empirical model to help in selecting a suitable window to optimize ECa measurement. Laboratory-determined ECa values obtained with the four-electrode method deviate up to 50% from the predicted values because of inappropriate selection of inter-electrode distances for the measurement. © 1990 Williams & Wilkins.