Abstract
ABSTRACT Quantification of the drained volume is one of the difficulties involved in using weighing lysimeters. Typically, this volume is measured by accessing a moat at the base of a lysimeter. However, it is not feasible to install the moat in small devices. Thus, the aim of this study involves developing, installing, calibrating, and checking the efficiency of small weighing lysimeters with automated drainage systems to test their functionality in field conditions. Each lysimeter is composed of a round PVC water tank with a diameter of 1.22 m and a depth of 0.58 m that is placed over a metal frame with three electronic load cells with the nominal capacity of each cell corresponding to 500 kg. The drainage system is composed of a small reservoir with a volume of 10 L, a weighing structure composed of a load cell with a nominal capacity of 30 kg, and an automatic solenoid valve driven by a device coupled to a data logger that records the data from the lysimeter and from the drainage system. Two calibrations are performed for the lysimeter as well as the drainage system to obtain equations with significant correlations (R2 > 0.9999). The drainage system was activated several times during the tests after receiving approximately 63.4 L of water from rainfall, and this in turn indicated a good performance.
Highlights
Evapotranspiration (ET) corresponds to the sum of evaporation (E) and transpiration (T) processes in vegetated surfaces that occur simultaneously, and it is often difficult to separate the two physical processes (Carvalho et al, 2007)
The present study aims to install, calibrate, and check the efficiency of weighing lysimeters with automated drainage systems to test its functionality in field conditions
The soil of the area is classified as Nitosol Red Eutroferric Latosolic, based on the Brazilian system of soil classification (EMBRAPA, 2006) that was in fallow at the time of the drainage systems calibration
Summary
Evapotranspiration (ET) corresponds to the sum of evaporation (E) and transpiration (T) processes in vegetated surfaces that occur simultaneously, and it is often difficult to separate the two physical processes (Carvalho et al, 2007). Weighing lysimeters include a device that is composed of load cells and a support structure that is used to measure the weight variation in a soil block placed inside a box, and the weight difference between income water (irrigation and rainfall) and outcome water (plant consumption and drainage) results in water consumption (Campeche et al, 2011). This type of a lysimeter provides reliable estimates if basic assembly requirements are satisfied (Allen et al, 2011), and it forms a standard method for calibrating other ET estimation methods (Faria et al, 2006). The drainage system of each lysimeter included a load cell ALFA® GL 30 model
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