Estimating unsaturated hydraulic conductivity of a sandy clay loam soil from Bulk density data
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Date
1997
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
The
Gardner
parameters
field
model,
K
Kgat/[1
+
(bhj"] ,
with
three
(Ksat, b, n) , was calibrated and validated with
dataforestimating
conductivityfora
the
sandy clay
unsaturatedhydraulic
insemi-arid
loam
soil
Dodoma, Tanzania.
Calibration of the model was achieved by measuring the in
situ saturated and unsaturated hydraulic conductivity at
different levels of bulk density (1.43,
1.64, 1.85 Mg/m3)
and matric suction (0.0, 0.2, 0.5, 0.8 and 1.0 kPa) using
the Disc Permeameter method which is a surface technique.
Ksat
was obtained from the graph of log(K,sat)
versus bulk
density. The parameters b and n were obtained by solving
the
simultaneous
equations obtained by measuring
different soil matric suctions.
K
at
For the sandy clay loam
soil at Hombolo, Ksat was obtained from the linear equation,
log(K3at ) = 5.644
2.164Qb and values of b and n are 0.66
and 1.32, respectively.
The model was validated using the Disc Permeameter method
by measuring the in situ unsaturated hydraulic conductivity
at different bulk densities
(ranging between 1.3 and 2.1
Mg/m3) and different matric suctions (0.2, 0.5, 0.8 and 1.0
kPa within the same range of bulk density) from the plots which initially were not used in the model
measurements.
calibration
The unsaturated hydraulic conductivity was
estimated from the same values of bulk densities used in
measuring the in situ unsaturated hydraulic conductivity by
using
the
calibrated
Gardner
model.
A
coefficient
of
determination (R2) = 0.997 was obtained when the estimated
unsaturated
hydraulic
conductivity values
against the ones measured in the field,
were
plotted
indicating that
easily measured soil characteristics such as bulk density
for
a
particular
soil,
can
be
used
to
estimate
hydraulic conductivity of that particular soil.
Description
Masters' Theses
Keywords
Sandy clay loam soil, Bulk density data, Unsaturated hydraulic conductivity