Calibration of the capacitance probe for soil moisture monitoring

Abstract

To obtain efficient use of water applied in irrigation, it is necessary to understand the dynamics of water in the soil, which is an important factor in agriculture. The aim of this study was to determine models for calibration and to evaluate thelysimetry methodwith undisturbed samples,using a capacitance probe for monitoring the moisture content of a TypicHapluderts soil under laboratory conditions. The predominant soil in the study area is from the TypicHapluderts soil unit. The soil samples were collected with undisturbed samples, in layers of 0 - 10 cm and 10 - 20 cm depth from the surface, using PVC pipes with a diameter of 315 mm and 600 mm height. The determination of the variation in soil moisture was carried out by weight difference (weighing lysimetry method). The measurements with a Frequency Domain Reflectometry (FDR) were made on a daily frequency and 6 repetitions per measurement. Analyzed calibration models (linear, potential and quadratic), was performed the Shapiro-Wilk normality test. The methodology used provided satisfactory results, with multiple repetitions being performed on the same sample. The model that showed greater precision and better fit for the two profiles under study was the quadratic model.