Dru Yates

Learning Objectives List and describe the 5 factors of soil formation List and describe the 4 soil forming processes Be familiar with common soil horizons and corresponding lowercase suffixes used to describe these horizons List and briefly describe the 10 soil orders in Canada Identify the diagnostic soil horizons for each soil order

Soil Classification: Why? Why? “…to organize the knowledge of soils so that it can be recalled systematically and communicated, and that relationships may be seen among soil properties and environmental factors, and among soil properties and suitabilities of soils for various uses.” NRC 1998

Soil Classification: How? How? We classify soils based on dominant soil forming processes. Wait…how do soils form???

5 Soil Formation Factors S = T(C,L,O,P) C = Climate (precipitation, temperature) L = Landscape (aspect, slope) O = Organisms (microbes, plants, insects…humans) P = Parent Materials (unconsolidated material in which soil formation occurs) T = Time that Parent Materials are subject to Soil Formation

Parent Material The foundation of the soil Transported or Residual Can influence: – pH – texture – fertility Weathering can be: – Physical – Chemical – Biological

4 Soil Forming Processes Additions Transformations Translocations Losses

Describing Soil Processes… What is being added? What transformations and translocations are taking place in this profile? What is being removed? How have C L O P at this site affected these processes over time?

- Organic matter – accumulation of OM; leaching of clay (eluviation) – accumulation of clay (illuviation); red-ox – accumulation of carbonates; less weathered R – unweathered rock

Describing Horizons Mineral horizons – A: surface horizon; eluviation and OM accumulation – B: “diagnostic horizon”; the next level of soil development – C: parent material; least amount of soil formation evident

Describing Horizons A suffix is needed to describe all but C and R horizons Common combinations: A – h, e, p B – h, f, t, n, m, v C – ca, s, sa, g

Describing Horizons Organic Horizons – LFH: folic (leaf) materials; measured as “above” the soil surface Litter Fibric Humic – O: peat materials; measured as “below” the soil surface Of - fibric Om - mesic Oh - humic Oco – coprogenous earth derived from aquatic origins

LFH or O? A? – accumulation of OM; leaching of clay (eluviation) B? – accumulation of clay (illuviation); accumulation of OM and Fe & Al oxides C? – accumulation of carbonates; cemented horizon R – unweathered rock

Canadian Soil Classification TaxaPrinciples UsedNo. of Classes OrderDominant soil forming process10 Great GroupStrength of soil forming process31 SubgroupKind and arrangement of horizons231 FamilyParent material characteristics~10,000 SeriesDetailed features of the pedon~100,000

The 10 Soil Orders – Regosolic Order Weak development Lack B horizon – Brunisolic Order Slightly developed “brown” soils Have a modified B horizon – Luvisolic Order Well developed “washed” soils Clays are eluviated downwards

Soil Orders – Gleysolic Order Well developed “gleyed” soils Fluctuating water table – Chernozemic Order Well developed “grassland” soils Organic matter accumulation within A horizon – Solonetzic Order Well developed “salty grassland” soils Similar to Chernozem, but with salt accumulations

Soil Orders – Podzolic Order Strongly developed “forest” soils Organic matter and iron/aluminum oxides accumulate in B horizon – Organic Order Matured organic soils Thick accumulation of decomposing organic matter – Cryosolic Order Moderately developed “frozen” soils Have a permafrost layer – Vertisolic Order Well developed “clay” soils Contain slickensides and argillopedoturbation

Cheat Sheet StepCriteriaResult 1Does soil have permafrost within 1 m of the surface or within 2 m if strongly cryoturbated? Cryosolic Order 2Does the soil have organic horizons (Of, Om, Oh) at least 40 cm thick (60 cm in the case of Of)? Organic Order 3Does the soil have both vertic and slickenside horizons within 1 m of mineral surface? Vertisolic Order 4Is there a podzolic B horizon (Bf, Bhf, or Bh at least 10 cm thick)? Podzolic Order 5Is there a Bg (or Cg within 50 cm of surface) at least 10 cm thick? Gleysolic Order 6Is solonetzic B (Bn or Bnt) horizon present?Solonetzic Order 7Is chernozemic A (Ah or Ap) present and >10cm?Chernozemic Order 8Is there a Bt horizon at least 5 cm thick?Luvisolic Order 9Is there a Bm, Btj, Bf, or Bfj at least 5 cm thick?Brunisolic Order 10Does this soil not meet any of the criteria above?Regosolic Order

Great Groups Canadian Classification of Soils… Humo-Ferric Podzol Great Group These soils have a Bf horizon thicker than 10 cm (or Bhf + Bf > 10 cm thick), organic C between 0.5 and 5%, and occurs at the drier end of the Podzolic range. Humic Podzol Great Group These soils are found at the wetter end of the range (either by region or landscape position) and have a Bh horizon thicker than 10 cm, and organic C > 1%. Ferro-Humic Podzol Great Group These soils occupy the intermediate position in the range. The Ferro-Humic Podzols have a Bhf horizon thicker than 10 cm and organic C >5%.