ABSTRACT
This paper describes the construction, installation and calibration of a weighing lysimeter in Paraipaba, State of Ceará, situated in Northeast of Brazil. The weighing lysimeter has a surface area of 2.2 m2, with a depth of 1.0 m, and was installed in order to determine the reference potential evapotranspiration for the region and adjust evapotranspiration models. The lysimeter is similar to a design developed by Kirkham and coworkers. A platform-type electronic scale was placed below the soil surface to measure the weight changes of the sol container. The calibration of the lysimeter was conducted applying mass amounts equivalent to 80 mm of water. The lysimeter was sensitive to mass changes of 400 g (equivalent to 0.18 mm) and with less than 1% total error over a range of 176 kg equivalent to the 80 mm of evapotranspiration. Correlatin betwcen applied standard mass and balance readings was linear (r2 = 0,9994).
Key words:
irrigation; evapotranspiration; lysimeter; calibration