Soils of the - Agriculture and Agri-Food Canada

BENSON SOILS (B)
Location and Extent : Benson soils are limited almost exclusively to lands along the north margin o f
Boundary Bay in south Delta Municipality. About 90 ha of pure map units and 130 ha of soil complexe s
dominated by Benson soils are mapped . The complexes are mostly with Mathews soils .
Topography and Elevation : Benson soils are slightly depressional to very gently undulating with slopes u p
to 2 percent. Elevations are all below 3 m above sea level .
Parent Material and Texture : Moderately coarse textured, stone-free Fraser River deltaic deposits are th e
parent material of Benson soils . Surface textures range from loam to sandy loam and generally becom e
somewhat coarser with depth . Some thin, silty, subsoil strata may be encountered .
Soil Moisture Characteristics : Benson soils are poorly to very poorly drained . They are rapidly to
moderately pervious and have moderate to low water holding capacity and slow surface runoff. The watertabl e
is usually near the surface during the winter but gradually retreats during summer causing droughty conditions .
Sea water readily seeps through the subsurface and subsoil sediments causing strongly saline conditions .
General Soil Description : Benson soils have a black or very dark gray, loamy, cultivated surface about 2 0
cm thick, often containing whitish salt crystals when dry. The surface layer is underlain by about 60 cm of gray ,
massive, weakly stratified sandy material which grades to greenish-gray, similarily textured material belo w
about 80 cm . Many, prominent yellowish, brownish and reddish mottles are present throughout (except in th e
surface layer) and salt crystals are usually evident in the subsoil . High levels of sulphides and sulphates are
usually present in the subsurface and subsoil . Soil reaction grades from medium or strongly acid in the surface
to extremely acid in the subsoil (1 :1 H 2 O) . Soil classification is Rego Humic Gleysol:saline phase.
Commonly Associated Soils : Mathews, Spetifore and Guichon soils are commonly associated wit h
Benson soils . Spetifore soils differ from Benson soils in that they are silty rather than sandy in texture . Guicho n
soils differ by consisting of about 50 cm of silty to clayey capping over sandy material . Both, however, are salin e
and poorly drained . Mathews soils, although similar to Benson soils in texture, are moderately poorly draine d
and non-saline .
Vegetation : Benson soils are all cleared . Where not recently cultivated, mainly salt tolerant grasses and herb s
occur. Rooting depth restricted to 60 cm or less by strongly saline soil conditions and high watertables .
General Land Use Comments : (1) Crops are mainly limited to forages because of high salinity and poo r
drainage during the winter. Watertable control and irrigation to leach the salts and alleviate summer drought ar e
required for satisfactory crop production . (2) Basements and other excavations are difficult to construct an d
maintain and septic tanks operate poorly because of high watertables . Corrosion of unprotected undergroun d
installations is likely because of strongly saline conditions and presence of compounds high in sulphur .
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