The Soils of Brant County - Agriculture and Agri-Food Canada

Ah horizon(dark brown or black)- Bm horizon(light brown)- Bt horizon(dark brown or reddish brown)- Bg horizon(mottled brown)-Cg horizon(mottled light brown)- Ck horizon(light brown)Figure 12 .Diagrammatic soil profile of a well-drained BrunisolicGray Brown LuvisolFigure 13 .Diagrammatic soil profile of a poorly drainedOrthic Humic GleysolThe C horizon has undergone little weathering and changefrom the original parent material . In Brant County it is generallymoderately to strongly calcareous .Well-drained soils develop on landforms having good surfacedrainage or on coarse textured materials with rapid internaldrainage .Imperfectly drained soils generally have the same type andsequence of horizons as well-drained soils, but are differentiatedby darker-coloured Ah horizons and the presence of yellowish or reddish-coloured mottles, and duller coloursthroughout the B horizon .Poorly drained soils are water-saturated for a sufficientperiod of time to cause reducing conditions indicated by thedevelopment of gray colours in the B and C horizons, and mottles often with prominent yellowish-brown colours . The Ahhorizon generally has a higher level of organic matter thanimperfectly or well-drained soils, hence is darker in colour, andusually thicker.Asketch of a poorly drained profile is shown inFigure 13 .Soil OrdersThe soil order is the highest category in the Canadian soilclassification system (11) . There are.nine soil orders in this system,four of them being represented in the soils of BrantCounty.Most of the well and imperfectly drained soils in Brant. County belong to the Luvisolic order. They have a soil profilesimilar to that shown in Figure 12 . These soils have a darkgrayish-brown organic enriched Ah surface horizon (Ap if cultivated)or are underlain by a grayish-brown Bm horizon . Thedark-brown, clay-enriched Bt horizon usually containsincreased concentrations of clay, iron and aluminum . Theunderlying parent material is calcareous and may be of glacialtill, lacustrine or glaciofluvial outwash origin .Soils of the Brunisolic order in Brant County may befound mainly on recent alluvium deposits within the floodplainsof the Grand and other river systems, on some sandytextured outwash or deltaic deposits . They have thick, dark AhorAp surface horizons rich in organic matter overlying brownishBm horizons that are not clay-enriched . The soil parentmaterial is moderately to highly calcareous and, in some cases,free carbonates may be present in all horizons .Regosolic soils in Brant County occur on small, localizedareas such as floodplains of the Grand River where they are ofrecent origin, or on severely eroded landscapes where the soilparent material is exposed . Profile development is minimal,characterized by a surface horizon with varying amounts oforganic matter enrichment underlain by slightly altered parentmaterials .Soils ofthe Gleysolic order are poorly drained and occupythe lowest positions in a landscape. The surface horizons areorganic-enriched and overlie prominently mottled gray orgrayish-brown horizons . The underlying parent material alsoexhibits dull grayish or brownish colours, and usually containsfew, if any, brightly coloured mottles (Figure 13) .Organic soils occur in very poorly drained depressionallocations favouring the accumulation of vegetative remains .They have an organic matter content in excess of 30 percent,and the organic material extends to a depth ofat least 40 cm .(Continuedonpage22)20