To determine soil shrinkage capacit

To determine soil shrinkage capacity and soil pore size
distribution, four additional soil cores were taken after the 3rd
drainage (at the filling stage, one week before harvest). The soil
cores were saturated for overnight and then equilibrated at a
sequence of water potential of 0.3 and 2.5 kPa with a sand box,
and then 10, 30, 100 and 300 kPa using pressure chambers
(Soil Moisture Equipment Corp., Santa Barbara, CA). After the
equilibrium at 100 kPa and 300 kPa, the soil cores were taken
out to measure the height and diameter using a vernier caliper at
five different positions on each core to determine the change in soil
core volume. The height was used to correct volumetric soil water
content and to calculate the shrinkage capacity. The shrinkage
capacity was characterized by using coefficient of linear extensibility
(COLE) (Grossman et al., 1968), which was calculated as the
one-dimensional change in the height of soil cores between
saturated and specific pressure (Eq. (3)).
COLE ¼ V0  Vx
Vx
 1=3
(3)
where, V0 and Vx are the volume of soil cores at saturation and at a
certain suction (100 and 300 kPa in this study).