Soils of the - Agriculture and Agri-Food Canada
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Soils of the - Agriculture and Agri-Food Canada

Soils of the - Agriculture and Agri-Food Canada Soils of the - Agriculture and Agri-Food Canada

sis.agr.gc.ca
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26.11.2014 Views

Location and Extent : Crescent soils are common on Westham and Crescent islands, in the southern part o f Richmond Municipality and southwest of Ladner There are about 990 ha of pure map units and 1040 ha of soi l complexes dominated by Crescent soils . Most complexes are with Westham and Ladner soils . Topography and Elevation : Crescent soils are usually nearly level or gently undulating with slopes les s than 2 percent minor areas are undulating with slopes to 4 percent . Land levelling has occurred in many areas . Elevations are all less than 5 m above sea level . Parent Material and Texture : The parent material of Crescent soils are medium to moderately fine textured , stone-free, deltaic deposits of the Fraser River, usually deeper than 1 m and underlain by saline sand . Surface , subsurface and subsoil textures are mainly silt loam, sometimes varying to silty clay loam . At depths of 1 m o r more, textures usually change to sand or loamy sand and at these depths a variety of sulphurous compound s are likely to be present . Soil Moisture Characteristics : Crescent soils are moderately poorly to poorly drained . They are moderately pervious and have slow surface runoff and high soil water holding capacity . The watertables are often nea r the soil surface during winter months but artificial drainage by ditches, subsoil drains and pumping is sufficien t to provide an adequate saturation-free rooting zone during most growing seasons . Some subsoil irrigation i s also possible by watertable control during dry summer periods . Saline conditions exist below about 120 cm bu t have little effect on most of the rooting zone . Almost all areas are protected by dykes from flooding during hig h tides and flood stages of the Fraser River . u- General Soil Description : Crescent soils have a friable to firm, dark grayish brown . silty, cultivated surface about 20 cm thick which is underlain by about 20 cm of dark gray . firm, silty material that breaks to prismatic o r blocky clods and contains many, yellowish-red mottles as well as thin clay skins and clay flows . This laye r grades to at least 50 cm of massive, silty material containing common, yellowish-red to dark reddish brow n 7 mottles and, in the lower part, hard . brownish tubules around old root channels . Underlying this is either gray to olive-gray, saline and sulphurous, fine sand or alternating lenses of sand and silt containing a few reddish - brown mottles and hard tubules . Soil reaction ranges from medium or strongly acid in the surface an d Plate 17 A landscape typical of parts of Richmond Municipality, Westham Islan d and western Delta Municipality. Crescent, Westham, Delta and Ladner soils are the usual soils developed in these nearly leve l to gently undulating poorly drained, silty to clayey deltaic deposits 60

subsurface layers to extremely acid in the sandy subsoil . Soil classification is mostly Orthic Gleysol. A few smal l areas of Orthic Humic Gleysol are included where the surface layer is grayish-black in colour . Commonly Associated Soils : Westham . Ladner and Delta soils usually occur in close association wit h Crescent soils . Westham soils differ from Crescent soils by having darker coloured surfaces, being somewha t more poorly drained and being saline between depths of 50 and 100 cm . Ladner and Delta soils differ by havin g substantially higher organic matter content in the surface : Ladner soils also have well developed cla y accumulation layers in the subsurface . Vegetation : All areas of Crescent soils are cleared and cultivated . Rooting is slightly restricted below about 25 cm by dense subsurface soil layers and is severely restricted below about 1 m by high watertable and salin e conditions . General Land Use Comments : (1) Crescent soils are considered to be among the best agricultural soil s in the Lower Mainland area . Almost all climatically suited crops can be produced . The soils are relatively fertil e although increased amounts of organic matter in the surface would help to improve structure and decreas e susceptibility to puddling . Watertables . in most cases . can be artificially maintained at more or less optimu m evels for good crop production . (2) Crescent soils are poorly suited for urban and related construction . Variabl e soil bearing capacities require special foundation considerations . Basements and other excavations are not practical because of high watertables and severe corrosion of unprotected underground installations is likel y due to saline subsoils containing high amounts of sulphur compounds . Septic tank effluent disc j ,. , `unction poorly because of high watertables and relatively slow soil permeability . Plate 18 Crescent soil profile (Orthic Gleysol) . These moderately poorly drained, silty soils have moderately structured layers (zon e between 1 and 2 ft. (30 to 60 cm) depth in photo) and are underlain by fine to medium, dark gray sand at depths greater than about 3 f1 . (90 cm)

subsurface layers to extremely acid in <strong>the</strong> s<strong>and</strong>y subsoil . Soil classification is mostly Orthic Gleysol. A few smal l<br />

areas <strong>of</strong> Orthic Humic Gleysol are included where <strong>the</strong> surface layer is grayish-black in colour .<br />

Commonly Associated <strong>Soils</strong> : Westham . Ladner <strong>and</strong> Delta soils usually occur in close association wit h<br />

Crescent soils . Westham soils differ from Crescent soils by having darker coloured surfaces, being somewha t<br />

more poorly drained <strong>and</strong> being saline between depths <strong>of</strong> 50 <strong>and</strong> 100 cm . Ladner <strong>and</strong> Delta soils differ by havin g<br />

substantially higher organic matter content in <strong>the</strong> surface : Ladner soils also have well developed cla y<br />

accumulation layers in <strong>the</strong> subsurface .<br />

Vegetation : All areas <strong>of</strong> Crescent soils are cleared <strong>and</strong> cultivated . Rooting is slightly restricted below about 25<br />

cm by dense subsurface soil layers <strong>and</strong> is severely restricted below about 1 m by high watertable <strong>and</strong> salin e<br />

conditions .<br />

General L<strong>and</strong> Use Comments : (1) Crescent soils are considered to be among <strong>the</strong> best agricultural soil s<br />

in <strong>the</strong> Lower Mainl<strong>and</strong> area . Almost all climatically suited crops can be produced . The soils are relatively fertil e<br />

although increased amounts <strong>of</strong> organic matter in <strong>the</strong> surface would help to improve structure <strong>and</strong> decreas e<br />

susceptibility to puddling . Watertables . in most cases . can be artificially maintained at more or less optimu m<br />

evels for good crop production . (2) Crescent soils are poorly suited for urban <strong>and</strong> related construction . Variabl e<br />

soil bearing capacities require special foundation considerations . Basements <strong>and</strong> o<strong>the</strong>r excavations are not<br />

practical because <strong>of</strong> high watertables <strong>and</strong> severe corrosion <strong>of</strong> unprotected underground installations is likel y<br />

due to saline subsoils containing high amounts <strong>of</strong> sulphur compounds . Septic tank effluent disc j ,. ,<br />

`unction poorly because <strong>of</strong> high watertables <strong>and</strong> relatively slow soil permeability .<br />

Plate 18 Crescent soil pr<strong>of</strong>ile (Orthic Gleysol) . These moderately<br />

poorly drained, silty soils have moderately structured layers (zon e<br />

between 1 <strong>and</strong> 2 ft. (30 to 60 cm) depth in photo) <strong>and</strong> are underlain by<br />

fine to medium, dark gray s<strong>and</strong> at depths greater than about 3 f1 . (90<br />

cm)

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