Soils of the - Agriculture and Agri-Food Canada

BLACKBURN SOILS .
(BB)
Location and Extent :
Blackburn soils occur only in the western part of Chilliwhack Municipality, mainly in the
vicinity of Arnold Station . There are about 70 ha of pure map units and 140 ha of soil complexes dominated b y
Blackburn soils . The complexes are with Pelly, Grigg and Henderson soils .
Topography and Elevation :
Blackburn soils are slightly depressional to gently undulating with slopes up t o
5 percent . In soil complexes, Blackburn soils usually occupy slightly higher topographic landscape position s
than Pelly soils and slightly lower positions than Grigg or Henderson soils . Blackburn soils lie between 5 and 1 0
m above sea level .
Parent Material and Texture : Blackburn soils have developed from moderately fine textured, stone-free ,
Fraser River floodplain deposits, mainly vertically accreted . The deposits usually contain thin, dark coloure d
lenses of buried, inter-flood organic matter accumulations . Surface, subsurface and subsoil textures are
generally silty clay loam with inclusions of silty clay . Textures usually change to medium or fine sand at depths o f
1 m or more .
Soil Moisture Characteristics :
Blackburn soils are poorly to moderately poorly drained . They are moderately
to slowly pervious, have high water holding capacity and slow to moderate runoff . The watertable is usuall y
near the surface during the winter but gradually retreats to at least 1 m during most summers . Surface wate r
temporarily accumulates in depressions during heavy rains .
General Soil Description : Blackburn soils have a very dark gray, friable, silty to clayey cultivated surfac e
about 20 cm thick . This is underlain by about 50 cm of grayish-brown, strongly vertically cracked, very firm ,
clayey material that grades gradually to 30 cm or more of massive, olive-gray, silty deposits . These, in turn, ar e
underlain by sandy materials at depths of 1 m or more . There are common to many yellowish-brown mottles an d
some dark grey, horizontal lenses throughout (except in the cultivated layer) . Soil reaction grades from strongl y
acid in the surface to medium acid in the subsurface and subsoil layers (1 :1 H 2 0) . Soil classification is Orthic
Humic Gleysol .
Commonly Associated Soils :
Arnold, Grigg, Pelly and Henderson soils are usually closely associate d
with Blackburn soils . Arnold soils differ from Blackburn soils in that they are silty rather than clayey in texture .
Grigg and Henderson soils differ by being imperfectly drained and contain well defined clay accumulatio n
layers . In addition, Henderson soils have a very deep (up to 80 cm thick) black, surface layer . Pelly soils are more
poorly drained than Blackburn soils and are often depressional in relation to them .
Vegetation :
The natural vegetation on Blackburn soils has essentially all been cleared and the soils are
cultivated . The few, small, remaining uncleared areas presently support mostly black cottonwood, vine maple ,
willow and a variety of shrubs . Rooting is restricted below about 60 cm depth by the dense, clayey subsoil an d
high groundwater tables .
General Land Use Comments : (1) Present utilization of Blackburn soils is mainly for forages and som e
field peas and corn . The range of possible crops can be substantially broadened through artificial drainage b y
controlling the watertable and removing surface water . (2) Variable soil bearing capacities and high watertable s
may require special road and building construction methods . Basements and other excavations are difficult t o
construct and maintain and are likely to contain water during parts of the year . High watertables and slow
permeability make Blackburn soils generally poor for septic tank effluent disposal . (3) Forest crops such a s
black cottonwood appear to be well suited for Blackburn soils . Potential wood production by this species i s
estimated to be between 9 and 12 m 3/ha/yr.
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