Abstract:
This study presents the design, construction and a field test of a microlysimeter. The
Microlysimeter consisted of four main components; an outer envelope, soil volume container, load
cell assemblies, and the electronic control system. The base of the Microlysimeter was sealed using
aluminum foil and rubber so that water loss will only be through evapotranspiration. The load cell
was installed at the bottom of the Microlysimeter assembly, and on top of it the soil volume was
placed in order to detect any loss of weight due to evapotranspiration. The change in weight is then
displayed on a display unit (Liquid Crystal Display) through the electronic control system. The
readings are then finally stored on the data logger. The system is powered by a 12V battery backed
up with a 52W solar panel. The field test of the constructed Microlysimeter was carried out in a
dry season of the year 2017, between 20/01/2017 to 25/01/2017. Measurements from the
Microlysimeter were compared with evapotranspiration estimates from Bowen Ratio-Energy
Balance (BREB) system installed at the West African Science Service Centre for Climate Change
and Adapted Land Use, (WASCAL), Meteorological Observatory enclosure, Federal University
of Technology Akure Ondo State, (7° 17’ 43.51’’N, 5° 08’ 55.21’’E at 390m above mean sea
level) Nigeria. Comparing the measurements from Bowen Ratio-Energy Balance (BREB) system
and the Microlysimeter, results show that the BREB system had hourly evapotranspiration values
16% higher than the Microlysimeter, although they both follow the same pattern and the fit
between the two data sets was good. The correlation coefficient (R = 0.683) value shows that there
is good correlation between the data obtained from the constructed Microlysimeter and Bowen
Ration-Energy Balance (BREB) system. Due to the availability of low-cost electronic sensors, it
is now possible to build an integrated microlysimeter system with capability for automatic data
logging locally to provide a reliable alternative to the manual observation in many meteorological
observatories. The automated Microlysimeter designed, fabricated and field installation has proven
to be a useful and effective tool in evapotranspiration study.
