Chapter 3: Key to Soil Orders

1. Soils that have permafrost within 1 m of the surface or within 2m if strongly cryoturbated… Cryosolic order
2. Other soils that either
   1. Have organic horizons (More than 17% organic C by weight) that extend from the surface to one of the following:
      
      1. A depth of 60 cm or more if the surface layer is fibric material (Of) having a bulk density of <0.075 g cm^-3.
      2. A depth of 40 cm or more if the surface layer consists of mesic or humic material (Om or Oh) having a bulk density ≥0.075 g cm^-3.
      3. A depth of more than 40 cm if composed of folic materials (L, F, and H), or at least 10 cm if a lithic contact or fragmental materials are present. Folic materials must be more than twice the thickness of a mineral soil layer if the mineral layer is less than 20 cm thick.
      or
      
      
   2. Have one or more mineral horizons or layers within 40 cm of the surface in addition to the organic horizons (O) as follows:
      
      1. If a mineral horizon or layer thinner than 40 cm occurs at the surface, the underlying organic horizon or horizons must have a total thickness of at least 40 cm.
      2. If one or more mineral horizons or layers occur within 40 cm of the surface, the organic material must occupy more than 40 cm of the upper 80 cm of the control section… Organic order
3. Other soils that have both a vertic horizon and a slickenside horizon, the top of which occurs within 1 m of the mineral surface… Vertisolic order
4. Other soils that have a podzolic B horizon and do not have a Bt horizon within 50 cm of the mineral surface… Podzolic order
5. Other soils that are saturated with water and under reducing conditions either continuously or during some period of the year as indicated either by direct measurements of the water table and the oxidation-reduction status, or by any of the following morphological features within 50 cm of the mineral surface:
   1. For all but red soil materials (hue 5YR or redder and color fades slowly on dithionite treatment).
      1. Chromas of 1 or less, without mottles, on ped surfaces or in the matrix if peds are lacking in materials that develop higher chromas under oxidizing conditions.
      2. Chromas of 2 or less, in hues of 10YR and 7.5YR, on ped surfaces or in the matrix if peds are lacking, accompanied by prominent mottles.
      3. Chromas of 3 or less, in hues yellower than 10YR, on ped surfaces or in the matrix if peds are lacking, accompanied by prominent mottles.
      4. Hues bluer than 10Y, with or without mottles, on ped surfaces or in the matrix if peds are lacking.
   2. For red soil materials (hue 5YR or redder and color fades slowly on dithionite treatment).
      1. Distinct or prominent mottles at least 1 mm in diameter occupying at least 2% of the exposed, unsmeared 10 cm layer… Gleysolic order
6. Other soils that have a solonetzic B horizon… Solonetzic order
7. Other soils that have a chernozemic A horizon and any one of the following:
   1. No Ae horizon.
   2. A weakly expressed Ae horizon (Aej) with a dry color value lower than 5.
   3. An Ae horizon thinner than an overlying Ah or Ap horizon that does not appear to be eluviated.
   4. An Ae horizon not more than 5 cm thick if the chernozemic A is eluviated (Ahe) as indicated by gray streaks and splotches when the soil is dry… Chernozemic order
8. Other soils that have a Bt horizon… Luvisolic order
9. Other soils that have either Bm, Btj, or Bfj horizons at least 5 cm thick, or a Bf horizon less than 10 cm in thickness… Brunisolic order
10. Other soils… Regosolic order

Source : The Canadian System of Soil Classification (Third Edition)