Soils of the - Agriculture and Agri-Food Canada

GRIGG SOILS (GG )
Location and Extent : Grigg soils occur only on the lowlands of the eastern part of the map area, south o f
Chilliwack Mountain . There are 55 ha of pure map units and 110 ha of soil complexes dominated by Grigg soils .
The complexes are mainly with Blackburn and Monroe soils .
Topography and Elevation : The topography of Grigg soils is undulating to gently rolling with slope s
between 3 and 8 percent . They lie between 7 and 10 m above sea level .
Parent Material and Texture : Laterally and vertically accreted, moderately-fine textured, stone-free, Frase r
River floodplain deposits form the parent material of Grigg soils . Surface and subsurface textures are usuall y
silty clay loam, varying sometimes to silt loam . The clay accumulation layer in the lower subsurface and uppe r
subsoil is mainly silty clay or clay. The lower subsoil is silty clay loam or silty clay, grading to medium or fine san d
below depths of at least 1 m .
Soil Moisture Characteristics : Grigg soils are imperfectly to moderately poorly drained . They are
moderately to slowly pervious and have high water holding capacity and moderate to slow surface runoff .
Winter watertables are high but retreat to below 1 m during most growing seasons . Where Grigg soils occupy
slightly depressional positions (in relation to adjacent soils), surface ponding commonly occurs during heav y
rains .
General Soil Description : Grigg soils generally have a surface consisting of 15 to 20 cm of dark gray, fir m
when moist and hard when dry, silty, cultivated material . The surface is underlain by about 20 cm of gray t o
grayish-brown, leached, silty material which is blocky, hard when dry and contains some reddish and'yellowis h
mottles . This grades to a clay accumulation zone about 40 cm thick composed of grayish, clayey material whic h
has strong blocky structure and is hard when dry and sticky and plastic when wet . It contains many reddish an d
yellowish mottles and clay flows and skins are well expressed . The clay enriched layer then grades to massive ,
gray, silty material below about 80 cm and loose, medium or fine sand below 1 m or more . Soil reactions var y
from strongly or very strongly acid in the upper layers to medium or slightly acid in the lower subsoil . Soi l
classification is Gleyed Gray Luvisol. In some moderately poorly drained, slightly depressional areas, the soi l
classification is Orthic Luvic Gleysol .
Commonly Associated Soils : Pelly, Blackburn, Arnold and Monroe soils commonly are closely associate d
with Grigg soils, either in soil complexes or adjacent map polygons . Pelly, Blackburn and Arnold soils all diffe r
from Grigg soils by being somewhat more poorly drained . They also do not have a well defined, subsoil cla y
accumulation layer. Monroe soils occupy slightly higher landscape positions than do Grigg soils and are wel l
drained .
Vegetation : All areas of Grigg soils have been cleared and are cultivated . Black cottonwood, willow and othe r
deciduous trees are common along fences and field boundaries . Rooting depth is mainly restricted to the uppe r
60 cm by the well-developed clay accumulation layer and periodically high watertables .
General Land Use Comments : (1) Most areas of Grigg soils are used for forage production and pastur e
as well as corn and field peas . Underdrainage to control winter and spring watertables assists in maintainin g
consistently high yields, especially of perennial crops . Subsoiling to open the clayey subsoil improves wate r
permeability and rooting depth . (2) Relatively low bearing strengths can potentially cause subsidence of heav y
structures while basements and other excavations will probably contain water through part of the year . Efficien t
septic tank effluent disposal is impaired by slow subsoil permeability and periodically high watertables . (3 )
Grigg soils seem moderately suited for forest crops such as cottonwood . This species is estimated to potentiall y
produce about 9 to 12 m3/ha/yr of wood on Grigg soils .
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