CALIBRAÇÃO DO SENSOR CAPACITIVO DE UMIDADE DO SOLO EC-5 EM RESPOSTA A GRANULOMETRIA DO SOLO

The accuracy of the capacitive sensors used to estimate the water content in the soil depends on the soil resources, requiring calibration for its correction. The objective of this study was to calibrate the EC-5 capacitive sensor to estimate soil water content in relation to different cerrado soil granulometry. Under laboratory conditions, the moisture variation of the Sandy Clay, Franco Sandy Clay and Clay soils was compared by the EC-5 sensor and the volumetric method. Samples were collected in the layers from 0.00 to 0.10; 0.10 to 0.30 and 0.30 to 0.50 m in central pivot areas in the Cerrado of Goiás. The soil was saturated and oven dried at 40oC to constant weight, this procedure was repeated three times. The statistical indices analyzed showed that the EC-5 sensor can be used for soil moisture determination and its calibration is required for each soil type. The sandy clay soil had a coefficient of determination (r2) greater than 0.95; for Franco sandy clay soil r2 was equal to or greater than 0.93 and for clay textured soil r2 was greater than 0.81. To calibrate the EC-5 sensor considering the clay content in the soil it is necessary to use the equation: θvol=0.0758-0.0023*Clay%-1.056* θEC-5.