Soils of the - Agriculture and Agri-Food Canada

COGHLAN SOILS (CG)
Location and Extent : Coghlan soils occupy a few areas south of Langley and in the vicinities of Hopingto n
and the Abbotsford Airport . There are about 310 ha of pure map units and 30 ha of Coghlan-Defehr soi l
complex .
Topography and Elevation : The topography of Coghlan soils varies from level or slightly depressional t o
very gently sloping . Slope gradients are less than 3 percent and elevations range from 30 to 50 m above se a
level .
Parent Material and Texture : Coghlan soils have developed from coarsetextured glaciofluvial deposits
which have small amounts of silty eolian material on or mixed into the surface . Surface textures vary fro m
gravelly sandy loam to loam and grade to gravelly sand or sandy gravel below about 20 cm . The surfaces are
moderately stony and a cemented layer is present below about 30 cm .
Soil Moisture Characteristics : Coghlan soils are imperfectly drained . They are rapidly pervious and hav e
slow surface runoff and low water holding capacity . The soils are subject to seepage accumulation from higher ,
adjacent areas and a fluctuating, perched watertable is present during periods of high precipitation .
General Soil Description : Coghlan soils have a dark gray to grayish-brown, friable, loamy, cultivate d
surface about 15 cm thick which is underlain by 5 to 15 cm of light gray, leached, sandy material containing a
few reddish mottles . This, in turn, is underlain by about 50 cm of yellowish-brown or reddish-brown, hard ,
strongly cemented, gravelly material which grades to loose, gravelly sand or gravel below about 80 cm . Soi l
reaction ranges from very strongly acid in the surface to medium acid in the subsoil . Soil classification is Gleyed
Ortstein Humo-Ferric Podzol.
Commonly Associated Soils : Defehr, Lehman, Columbia, Abbotsford and Lynden soils are usuall y
closely associated with Coghlan soils . None, however, have cemented subsurface layers . Defehr and Lynden
soils differ also by being sandy rather than gravelly in subsoil texture . Lehman soils are poorly drained whil e
Abbotsford soils have silty surface and subsurface layers and are well drained .
Vegetation : Most areas of Coghlan soils are cleared and cultivated or used for urban purposes . Uncleare d
areas support a variable forest of western red cedar, western hemlock, red alder, willow, birch, black cottonwoo d
and vine maple . Rooting depth is moderately restricted below about 40 cm by cemented soil layers .
General Land Use Comments : (1) Coghlan soils are limited for agriculture by low fertility and low wate r
holding capacity ; these can be improved by adequate fertilization and irrigation . The fluctuating watertables ,
particularly present during high rainfall periods, are harmful to perennial crops and some watertable control i s
beneficial . (2) Coghlan soils are moderately to poorly suited for urban and related development . High periodic
watertables make basement and other excavations difficult to excavate during portions of the year and they ar e
likely to contain water for varying periods . The operation of septic tanks is impaired during high watertabl e
periods and incomplete filtration by the coarse-textured subsoils may potentially contaminate groundwater . (3 )
Coghlan soils seem moderately suited for forest production . Estimated yearly growth of western red cedar is 7 t o
9 m 3 of wood/ha .
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