Water and soil redistribution in a cultivated Saskatchewan landscape
Date
2003
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Doctoral
Abstract
The concept of topographically controlled moisture redistribution underlies the
conceptual model of soil development used by most researchers in the semi-arid
northern Great Plains. The first part of this study explores the variability in the process
of soil moisture redistribution, and its spatial distribution as it may be linked to
topographic or pedogenic attributes. Recent advances in tillage research have shown
that within cultivated landscapes tillage-induced redistribution of soils is the dominant
erosion mechanism. The second part of this study attempts to validate the new model of
tillage redistribution under Saskatchewan conditions.
The redistribution of soil moisture was monitored on three occasions between
June 1997 and October 1998 using the redistribution of a chloride tracer as a surrogate
for moisture redistribution. The results of the chloride tracer provided clear evidence for
the direction and magnitude of water flow during the study period. The results confirm
the distinction in the moisture redistribution process between depression-centred soils
and upland soils. The primary control on the movement of the tracer at depression-centred
soils was spring flooding in early 1998. Subsequent redistribution of the
remaining tracer was dominated by discharge phenomena. Subsurface flow in upland
soils is clearly anisotropic, with observed differences in the degree of lateral and vertical
redistribution of the chloride mass between landform elements and between soil profile
classes.
Two tillage experiments were conducted to evaluate the tillage process under
Saskatchewan field conditions. The results of the tillage experiments were compared
with the medium to long-term soil redistribution history as derived from cesium-137
redistribution. The cesium-137 results clearly show that the field-scale pattern of
erosion at this Saskatchewan site corresponds to the characteristic pattern for tillage-induced
erosion. Experimentally determined erosion values largely match or exceed those derived from the cesium-137 redistribution.Cesium-137 derived erosion rates for divergent shoulders, divergent backslopes and convergent backslopes were 42.3, 32.4, and 10.8 Mg ha-1 y-l, respectively.
Experimentally determined values for net tillage erosion in these landform elements
using a surface applied granular tracer and the median slope gradient for each category were 44, 74, and 86 Mg ha-1 y-l, respectively. Net erosion values determined using an
aqueous tracer applied to the soil surface had values of 16, 28, and 32 Mg ha-1 y-l for
divergent shoulders, divergent backslopes and convergent backslopes respectively. The
comparatively low net erosion value for the divergent shoulder landform elements in the
second experiment reflects the lack of a slope curvature factor in the erosion calculation.
These results confirm that the redistribution of water and the redistribution of
soil materials by tillage are the basic controls on the distribution of soil taxa in this
landscape.
Description
Keywords
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Soil Science
Program
Soil Science