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Soils of the - Agriculture and Agri-Food Canada

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LUMBUM SOILS (LM)<br />

Location <strong>and</strong> Extent : Lumbum soils occur throughout <strong>the</strong> upl<strong>and</strong>s <strong>and</strong> lowl<strong>and</strong>s <strong>of</strong> <strong>the</strong> report area . The<br />

largest areas, however, are found on <strong>the</strong> lowl<strong>and</strong>s <strong>of</strong> Richmond, Delta <strong>and</strong> Surrey Municipalities . About 2830 h a<br />

<strong>of</strong> pure map units <strong>and</strong> 1950 ha <strong>of</strong> soil complexes dominated by Lumbum soils are mapped . The complexes are<br />

mostly with Triggs, Glen Valley, Lulu, Gibson <strong>and</strong> Judson soils .<br />

Topography <strong>and</strong> Elevation : The usual topography <strong>of</strong> Lumbum soils varies from level to very gently slopin g<br />

or gently undulating with slopes less than 2 percent . Elevations range from 1 to 100 m above sea level .<br />

Parent Material <strong>and</strong> Texture : Lumbum soils have developed from deep, partially-decomposed, organi c<br />

deposits at least 160 cm thick . Surfaces vary in decomposition, ranging from essentially undecomposed (fibric )<br />

in some uncleared areas to well-decomposed (humic) in areas that have been cultivated for a number <strong>of</strong> years .<br />

Subsurface <strong>and</strong> subsoil organic material is partially-decomposed (mesic) <strong>and</strong> is derived from mixtures o f<br />

sedges, reeds <strong>and</strong> moss . The underlying mineral sediments are usually ei<strong>the</strong>r clayey deltaic, silty floodplain o r<br />

clayey glaciomarine deposits . The deltaic deposits are usually saline. In a few areas, varying amounts <strong>of</strong><br />

surface organic material have been removed by peat harvesting .<br />

Soil Moisture Characteristics : Lumbum soils are very poorly drained . They are moderately pervious an d<br />

have very high water holding capacity <strong>and</strong> slow surface run<strong>of</strong>f . The watertable is near, <strong>and</strong> sometimes at, <strong>the</strong> soi l<br />

surface for most <strong>of</strong> <strong>the</strong> winter <strong>and</strong> during heavy, prolonged, summer rains . Surface ponding is likely durin g<br />

<strong>the</strong>se times .<br />

General Soil Description : The surface <strong>of</strong> Lumbum soils in cultivated areas consists <strong>of</strong> partially-decomposed,<br />

black to dark reddish brown, friable organic material about 20 cm thick . In uncleared area, it consists <strong>of</strong><br />

about 20 cm <strong>of</strong> yellowish-red to dark reddish brown, spongy, weakly to partially decomposed material . Th e<br />

surface layer is underlain by at least 140 cm <strong>of</strong> dark reddish brown to dark brown or yellowish-brown, weakl y<br />

stratified, partially-decomposed (mesic) organic material varying in composition from sedge <strong>and</strong> reed remain s<br />

to mostly moss . The degree <strong>of</strong> decomposition generally increases with increasing depth <strong>and</strong> occasional pieces<br />

<strong>of</strong> wood are usually scattered throughout . Soil reaction is extremely acid throughout . Soil classification is Typic<br />

Mesisol .<br />

Commonly Associated <strong>Soils</strong> : Lulu, Triggs, Gibson <strong>and</strong> Judson soils <strong>of</strong>ten occur in close association with<br />

Lumbum soils . Lulu <strong>and</strong> Gibson soils differ from Lumbum soils by consisting <strong>of</strong> between 40 <strong>and</strong> 160 cm o f<br />

partially-decomposed organic material over mineral sediments . The mineral subsoils <strong>of</strong> Lulu soils are usually<br />

saline while those in Gibson soils are non-saline . Judson soils differ from Lumbum by consisting <strong>of</strong> 40 t6160 c m<br />

<strong>of</strong> well-decomposed organic material over mostly glaciomarine deposits . Triggs soils differ by consisting o f<br />

deep, undecomposed, organic deposits composed mainly <strong>of</strong> moss .<br />

Vegetation : Uncleared areas support a variety <strong>of</strong> plants, including birch, shore pine, western red cedar,<br />

western hemlock, red alder, Labrador tea, bracken, blackberry, salai, sedges <strong>and</strong> several mosses . Rooting is<br />

mostly restricted to <strong>the</strong> upper 50 cm by <strong>the</strong> high, groundwater tables .<br />

General L<strong>and</strong> Use Comments : (1) <strong>Agri</strong>culturally, Lumbum soils are limited by high watertables an d<br />

extreme acidity. Acidity can be improved by liming, <strong>the</strong> amount required dependent on <strong>the</strong> crops grown .<br />

Artificial drainage is required to control <strong>the</strong> high watertables . Watertable control should be sufficient for th e<br />

crops grown ; overdraining is likely to cause undue subsidence <strong>and</strong> decomposition . Low bearing strengths ma y<br />

require "flotation-type" <strong>of</strong> equipment for cultivation . (2) Urban <strong>and</strong> related uses are not suited for Lumbum soils .<br />

Low bearing strengths are likely to cause severe foundation problems, periodic flooding is possible an d<br />

basements <strong>and</strong> similar excavations are not possible due to high watertables . High groundwater also make s<br />

septic tanks unsuitable for sewage disposal .<br />

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