Calibração de sensores dielétricos ECH2O para solos de referência na Zona da Mata de Pernambuco

Abstract

The efficiency in the management of irrigation depends, among other things, instruments of soil moisture measurements, in order to rationalize the use of water and energy and maximize crop yields. The aim of this study was to calibrate the dielectric sensors ECH2O EC-5 and 5TE models (Decagon Devices, Inc. ™) to reference soils located in Pernambuco Forest Zone: Espodossolo Humilúvico (EK), Argissolo Amarelo (PA), Latossolo Amarelo (LA) e Argissolo Vermelho-Amarelo (PVA). The experiment was conducted in a greenhouse of UFRPE, Recife-PE. Samples were collected with deformed and non-deformed structure at a depth of 0-40 cm. In the laboratory, samples were deformed structure were crushed and passed through a 4.75 mm sieve taken from roots and then placed in six plastic pots with a volume of 4.66 L each, in order to maintain their density of the soil in the field. The bottoms of the containers have previously been drilled, lined with crushed stone and covered with bidim felt in order to permit drainage of excess water, preventing soil losses. Four pots were installed a sensor of each model and the other pots only EC-5. The sets (pot, soil, gravel, bidim and sensors) were weighed three times daily at a fixed time (8h, 12h and 16h), until the stability of moisture. During this period they were performed hourly readings of soil moisture measured by moisture sensors, m3 m-3, by data collection stations EM50 (Decagon Devices Inc ™). The results were submitted to regression analysis comparing sensors readings with volumetric moisture calculated based on the gravimetric moisture. Performing statistical indices were used to assess the efficiency of the proposed model. The statistical index Willmott and RMSE were used to evaluate the quality of fit between observed and estimated values. The EC-5 sensor showed a linear response for all soils and the 5TE showed a linear response in three of the four soils. The results showed that the calibration improved the performance of sensors reducing RMSE, in EK soil of 0.0552 to 0.0112 the EC-5 and 0.0821 to 0.0198 of the 5TE; in PA from 0.0678 to 0.0223 to the EC -5 and from 0.0873 and 0.0207 for the 5TE; in LA from 0.0672 to 0.0173 to the EC-5 and 0.0709 to 0.0138 to the 5TE; and PVA from 0.0402 to 0.0208 to the EC-5 and from 0.0544 to 0.0227 to the 5TE; Willimott index found were d = 0.99 for EK, d = 0.98 for PA, d = 0.99 for LA and d = 0, 98 for PVA, all classified as great.