Evaluation of low-cost electronic sensors for monitoring soil moisture in an experimental area in the Brazilian semiarid.

Purpose: This paper aims to determine and evaluate the calibration curve for low-cost electronic sensors in soils from a reclaimed and degraded area in the Brazilian semiarid region. Design/methodology/approach: The probes were made, programmed and inserted in soil previously conditioned in polyethylene cylinders. The sets "cylinder + probe + soil" were subjected to saturation for a period of 24 h and, subsequently, gravitational drainage at room temperature and daily weighings were performed. When the set reached constant weight, the samples were taken to dry in an oven at 105°C to determine the dry mass and later, determine the gravimetric moisture and convert it into volumetric. The volumetric moistures obtained were related to measured frequency variations and the adjustments were analyzed by regression, which was subjected to analysis of variance (p = 0.05), and related by a third-degree polynomial equation whose quality of the fit was verified with coefficient of determination (R2). Findings: The obtained moistures were related to the estimated moistures and evaluated by the root-mean-square error and straight 1:1. The results demonstrate that the sensors are not accurate for moistures in saturation, but representative and statistically acceptable results for moistures up to field capacity. Originality/value: This paper has not been published before in its current, or similar form. [ABSTRACT FROM AUTHOR]