Jaron Wiigs

@wiigs

In my soil work I have heard about or encountered other soil classification systems, namely the US system, which is also broadly used in countries that haven’t yet created their own system.

Organic layers of mineral soils focus more on the degree of decomposition, a more biological approach. This is an LFH layer which stands for Litter, Fibris, and Humus. It occurs on forest floors due to leaf buildup.

I felt I should make this post to demonstrate where my strong points in terms of soil might be, and also where I would like to improve. Out of all classification systems I have encountered besides Canada’s, the US system is what I would like to learn most. This is because the US system focuses more on the mineralogy of soils.

A chunk of a Cg horizon that I found alongside one of the greatest soil scientists in Canada. What was interesting about this chunk is that it has both Iron mottles (light orange caused by oxidation of iron, a characteristic of a “gleying” wet and dry cycle) and pure unoxidized iron mineral (dark orange).

In Canada, we do focus on particle size extensively, as texture is an extremely important step in classifying the physical processes acting on the soil, as having an influence on determining the parent material.

Canada’s texture (particle size) classification scale.

In Canada’s system, the closest thing we have to classifying soil chemical properties in the field is the lowercase horizon suffix k, denoting the presence of carbonates, which hints at eluviation processes acting on the soil, as well as a glacial till parent material.

The k suffix can be added by testing a horizon with a drop of acid and watching for bubbling. This denotes the presence of carbonates. The n suffix is another that can only be confirmed confidentially with lab testing.

We do have the f lowercase suffix for soil horizons, which depends on the presence of certain ratios of pyrophosphate, iron, aluminium, and organic matter, but these can only be confirmed with lab testing.

Soil horizon classification focuses mostly on physical processes, for example the e lowercase suffix denotes downward eluviation of some material. One of the only lowercase suffixes that requires laboratory testing is the f suffix. The ca suffix denotes secondary carbonate enrichment, and must be tested in a lab beside the primary carbonate horizon.

In the US system (and most of the world, because many countries use the US system), mineralogy and chemistry is focused on much more. In drilling and core sampling projects at my work, we use the US system. I hope to explore some of these projects to improve my understanding of soil mineralogy and chemistry in the near future.

Drill cores I found online. Drilling projects usually run deeper than soil surveys, and are more based on mineralogy.

Overall, Canadian soil science is more based around physics, with some chemistry involved. The Canadian system of soil classification is available for free online in PDF form here. As always, if any information presented in this post is wrong or you have anything to add, please contact me! I am always trying to learn more.

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