CALIBRATION OF A WEIGHING LYSIMETER FOR MEASURING COCOA EVAPOTRANSPIRATION

• Autor(a) principal: Silva, Gerlange Soares da
• Data de Publicação: 2020
• Outros Autores: Pereira, Francisco Adriano de Carvalho, Santana, Rodrigo Almeida, Meneses, Thaís Nascimento, Lopes Sobrinho, Oswaldo Palma, Rosário, Alex Santana do
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Revista Caatinga
• DOI: 10.1590/1983-21252020v33n324rc
• Texto Completo: https://periodicos.ufersa.edu.br/caatinga/article/view/9105
• topic: Theobroma cacao L. Instrumentação agrícola. Demanda hídrica de culturas.; Theobroma cacao L. Agricultural instrumentation. Crop water demand.

Well-operated and calibrated weighing lysimeters reliably determine the water demand of agricultural crops, and the quality of the data is evaluated through the error analyses attributed to the instrument. The objective of this study was to determine performance parameters of a weighing lysimeter and to evaluate its adequacy for the direct determination of cocoa crop evapotranspiration. The lysimeter with 1.44 m2 surface, supported on four load cells installed in the experimental area of the Graduate Program in Agricultural Engineering of the Universidade Federal do Recôncavo da Bahia, was calibrated at 3:00 a.m., using known masses at intervals of 02 minutes in five cycles of addition and removal. Data were collected using a datalogger coupled to four load cells with an individual capacity of 1000 kg, programmed to perform readings every 01 second, storing the averages of 15 minutes. The lysimeter showed excellent accuracy, with r2 greater than 0.99 in the correlation between the standard masses and the signal of the load cells and standard error of linear regression estimate of 0.03 mm. The combination of repeatability and hysteresis errors with an uncertainty of 0.19% showed that the load cells have accuracy of ±0.07 mm, with resolution of 0.00033 mV, and sensitivity to detect mass changes below 0.1 mm, the system is adequate for direct measurement of cocoa ETc at time intervals of less than one hour.