How to Read a Soil Monolith

Whenever soil scientists or land managers are attempting to classify a particular soil, they first identify the parent material and all horizons within the soil profile. Based on the information gathered, they then decide on the diagnostic soil horizon, which helps them classify that particular soil within a specific soil order. In short, soil scientists and land managers follow tasks 1, 2, and 3 outlined below.

To help you master each of the three tasks, here are a brief instructions and associated guiding questions. Please note that these are equally relevant for soil identification and classification done in the field or in the lab by using a soil monolith.

TASK 1: Identify soil parent material

Focus your attention at the bottom of the soil monolith (or profile if you are in the field) and try to determine type of parent material. Consider the following questions:

  1. What are the most noticeable characteristics of the parent material identified?
    1. Is the parent material coarse or fine-textured?
    2. Are there any coarse fragments (with diam. > 2 mm) present? If so, what is their degree of rounding (angular, sub-rounded, rounded)?
    3. What is the degree of sorting (are particles all the same size, or do they range in size)?
    4. Are there any layers or varves present?
  2. What was the mode of transportation and deposition for the parent material identified?
TASK 2: Identify soil horizons

After you have identified the parent material, focus your attention to the soil above it and try to identify soil horizons. For each horizon identified, answer the following questions:

  1. Is the soil horizon mineral or organic?
  2. What is the horizon thickness?
  3. If the horizon in question is mineral, are individual mineral particles visible by a naked eye?
  4. What is the type of soil structure?
  5. What is the horizon colour?
  6. Are there any mottles present?
  7. How does this horizon differ from overlying and underlying horizons? Note differences in colour, texture, structure, rooting depth, etc.
  8. What is the most dominant soil formation process in this particular horizon?

Overall question regarding the soil horizons identified:

  1. What is the diagnostic soil horizon for this soil?
TASK 3: Classify the soil

Based on the information gathered during tasks 1 and 2, classify the soil.

  1. To what soil order (and great group), within the Canadian soil classification system, does the soil belong?