| dc.description.abstract | The study evaluated the Soil Moisture.
Retention, Release and Saturated Hydraulic
Conductivity, (Water Movement), in 6 Kenyan soils
that included: 1 Andosol, 1 LuvisoljAcrisol,
1 Arenosol, 2 Nitosols and 1 Vertisol. Further
investigations were carried out to establish the
relationship between the three parameters and the
selected soil characteristics.
Simple linear correlations showe d that
Saturated Hydraulic Conductivity was mainly a:
function of the Fine Silt and Medium Sand fractions
of the soils studied and that the Total Sand and
Coarse Silt Fractions became important down the
profiles. However, ':L'otal Sand had a negative
effect in the 30-36 cm depth. Ksat was mainly
reduced by the Clay fraction, particularly the
Montmorillonitic type.
Moisture Retention was mainly increased by
the finer textural fractions of Clay, Medium Sand
and Medium Silt. oran t c Matter also was
associated with high Moisture Retention.
The coarser textural fractions namely, Total
Sand and Fine Sand, reinforced by the Bulk Density
were associated with Lower Moisture Retention at
specified suctions.
Soil Moisture Storage between Specified
reference suctions was positively related to Total
Silt, Medium Silt and Organic Matter Content. Low
Soil Moisture Storage was related to high Bulk
Density, Total and Fine Sand fractions. At very
low suctions (0.1-1 bar), the Moisture Storage was
positively correlated with Total and Fine Sand
fractions whereas, at higher suctions, (0.3-1 and
1-15 b ar ranges), the Total Sil, and nedium 5=-1::.
enhanced SMse.
The overall Moisture Release, (RSe
O
_1S)' was
positively influenced by the Fine Silt, Fine Sand
and Total Silt in the 0-36 cm depth whereas the
Total and Fine 'Sand were dominant in the 60-66 cm
depth. The Clay fraction and Organic Matter had
negative effects on the. RSeO_lS with such
magnitudes that increased down the profiles.
The Moisture Release low suctions, (0-1 bar),
was a function of Total Sand and Fine Sand where
as at higher suctions, (1-15 bars), it was a
function of the Total Silt, Medium Silt, Organic
Matter and Fine Silt. Lower RSe in the same
range was associated with high Bulk Density and
the Sand fractions.
High gradients of the moisture retention
curves were attributable to high Sand fractions
reinforced by Bulk Density while the lower
gradients were related to higher Clay, Organic
Matter and the Silt fractions.
Moisture release curves with high gradients
were often associated with high Total Sand and
Fine Sand at low suctions while at high suctions
the Silt and Organic Matter content dominated.
Bulk density and the Sand fractions led to lower
gradients at high suctions.
The Clay Mineralogy variations did not
feature very prominently in the study and most
observations could be attributed to Texture,
Organic Matter and Bulk Density, with strong
indications of the structural influence.
Subdivision of the main textural fractions
of Sand and Silt improved the soil moisture
evaluations in this study.
In the overall soil moisture status
evaluation) K sat was considered a vital link
between the SMse and Rse as far as the potential
moisture availability to both plants' and other
varied soil life forms is concerned. Emanating
from the study was the possibility of basing
soils' potential productivity evaluations on
their ability to release moisture. | en |
