WHAT IS A LYSIMETER
Lysimeters are a method used to study
percolation and leaching losses of soil. One type is called a plate
lysimeter where water first moves down through undisturbed soil, then through
sand and gravel on an inclined slope and goes into a collection container.
This leachate is finally pumped to a collection vesicle. We use
a second type of called suction lysimeters. These suction lysimeters
have an advantage over tile-drain systems found with plate lysimeters in
that variations in a large area or field are avoided and numerous lysimeters
can be used in a controlled experiment in which different soil-plant management
systems are compared. In our case we are able to compare ferilized
with unfertilized second growth forest soils at different depths. Our
shallowest lysimeter is a simple pan that collects water after passing through
the canopy and the forest floor. It is generally only a few centimeters
below the forest floor surface (Brady and Weill 2002).
The other lysimeters are deeper and suction (also
called negative tension) lysimeters that collect water from 15 cm to 1 m
depths. To investigate the soil and to install lysimeters we first
dig a 0.25 meter squared pit (Figure 1). Soil Weights of soils are
determined at different depths as the soil is removed from the cubed pit
(Figure 2). A borer is used to core holes into the sides of the pits
and then PVC tubes with porous cups attached are inserted into the cored
holes and backfilled with native, sieved (25mm) soil.