Field Evaluation of a Capacitance Soil Moisture Sensor to Obtain Irrigation Scheduling Parameters

Abstract

Capacitance soil moisture sensors have been widely used to measure soil water content. However, their accuracy for field application is rarely investigated in comparison with other conventional methods. To evaluate the performance of a capacitance soil moisture sensor (EC-5, Decagon device), two side-by-side soil moisture profile measurements, which were acquired from 70 cm depth using the EC-5 and tensiometers under film mulching are compared from July to September in the years 2011 and 2012 at an Andisol site in Japan, were compared. Soil moisture readings by the EC-5 coincided with those by tensiometers in the moisture range below 78 kPa. Tensiometers could not measure moisture levels above 78 kPa; however, the EC-5 was capable of measuring moisture levels above 78 kPa. Parameters for irrigation scheduling (daily consumption rate, soil moisture extraction patterns and total readily available moisture) were estimated using the data acquired from both the EC-5 and tensiometers. These parameters almost coincided with each other, except in the dry period. Therefore, we concluded that the EC-5 can accurately measure soil moisture in the field and provide useful parameters for irrigation scheduling.