Calibración de sensores de humedad del suelo para estimar el contenido de agua en el Campus Irquis de la Universidad de Cuenca

Abstract

Soil moisture content is a parameter widely used in soil science and, at present, multiple technologies have been developed to estimate it as those based on Time Domain Reflectometry (TDR) as a tool to monitor water content. The objective of this study was to obtain a calibration equation of two types of TDR's: CS655 and TRIME FM, for the soils of the Irquis experimental farm of the University of Cuenca. This study was developed at the plot level, for which, three areas of 25 m2 were defined. The evaluated treatments included: i) TDR (CS655) for continuous measurement, ii) TDR (TRIME FM) for manual measurement, and iii) gravimetric method. Each treatment was evaluated under three repetitions and at three depths: a) 0 - 20, b) 20 - 40 and c) 40 - 60 cm. The monitoring period was 30 days. A representative calibration equation for the continuous TDR CS655 (VGRA = 0.2084VTDR - 0.3628) was obtained by comparing the volumetric content recorded by the TDR (VTDR) with the laboratory gravimetric volume. An adjusted coefficient of determination (R2aj) of 0.476 was obtained for plot 1 (depth of 0 - 20 cm) being the highest correlation among all three plots. Calibration equations show very low results (R2aj between -0.033 a 0.117) for the depth of 20-60 cm, because during the development of this research the soil of the study area remained saturated at that depth. It is concluded that this calibration equation can be used to monitor soil moisture content in the arable layer under these soil conditions; and because there is no greater variation in their morphological properties with respect to depth within each study area, the same equation could be used for deeper layers. However, it is inappropriate to use this equation for the depth of 20 - 60 cm because the soil remains saturated.