LISÍMETRO DE PESAGEM E DE LENÇOL FREÁTICO DE NÍVEL CONSTANTE PARA USO EM AMBIENTE PROTEGIDO

Abstract

This paper had as objective to build and to calibrate weight lysimeters of low capacity and to establish comparisons between the working status of constant level water table lysimeters. Two weight lysimeters of 15-L and 50-L and two constant level water table lysimeters of 15-L and 50-L were built at Embrapa Mandioca & Fruticultura Irrigation and Fertirrigation Laboratory, Cruz das Almas - BA, Brazil. Linearity, repetitivity and hysteresis errors in the range of reading of the weight lysimeter. Simultaneously measurements of soil evaporation were performed on bare soil with the two lysimeters in a 1-h interval. Afterwards, orange transpiration was measured by using lysimeters and by using a heat balance sap flow equipment. Results showed that the relation between analogical signals and the standard mass in the lysimeter provided linear equation with reasonable goodness of fit. The systematic and random errors were larger in the lysimeters of larger capacity. The instruments were able to make readings with good stability during the days of measurements and were also able to detect mass variation due to hourly transpiration. However, the measurements were in agreement if comparing average three day data.