Soil Organic Matter (SOM) – The Principle Focus Of Soil Health

Staying a little divergent from the norm – I want to interject some of my own observations & thoughts in soil health/quality, although not really my own as my knowledge base has been built up for many years by so many folks that are much smarter than I am.

I’ve put together one of my own “fact sheets” regarding soil organic matter (SOM) and I’ve been refining it a bit in the last few weeks. I know what you’re thinking: We have fact sheets coming out our ears, why do we need another? Well, we don’t necessarily. I’ve just been giving out my version locally to students and what not. But, with the attention other folks have been giving SOM lately, I figured I’d link to several SOM references out there in order to drive home this point: Soil health/quality begins and hinges on this one basic factor – Soil Organic Matter. It is the number one driver of a healthy soil. I suppose it could be argued that soil biological activity is THE most basic factor, and I wouldn’t really argue with that. They are so intertwined that they really are not separable, you can’t have one without the other.

Many things effect soil health, or non-health. Some are inherent properties such as texture, mineralogy, depth (to bedrock or other restrictive layer), geographical climate (precipitation, temperature), rocks, and land form/aspect. These conditions or properties are quite difficult to change. However, ALL of them can be modified to some extent by human manipulation.

From a strict “industrial ag” perspective we manage the soil like a chemistry set, adding specific chemical nutrients to make up for a deficit we see in a standard soil test (or a deficit in a tissue sample, after the fact).

Looking at it from the perspective of sustainable/regenerative agriculture, SOM is what we are managing for – striving to increase it as much as we can. Why? SOM has so much influence on virtually every other factor, property, or indicator of soil health, including those inherent properties mentioned above. If your SOM levels (and biological activity) are high, all other balances (systems, processes, cycles, etc.)  seem to “self regulate”.

The several links below are fact sheets and other reference material that I highly recommend regarding SOM.

I made my SOM fact sheet for the average joe, with just a little scientific”ese”.  I was trying to come up with a concise explanation with some detail, but not too much… yeah, that’s kind of a fuzzy target isn’t it?

NRCS Soil Quality Technical Note No. 5 – Managing Soil Organic Matter. As an assigner of T to soil map units/components I totally agree with managing for “C”, NOT for “T”. Any soil loss should not be tolerated if we are truly conserving the resource.

Rudy Garcia’s colorful and complex flow chart regarding SOM and it’s management. A bit busy, but take some time to study it and it’s quite informative.

Soil Organic Matter fact sheet from the Soil Quality Test Kit “bucket” for educators. Developed in Nebraska as a simpler educational version to the regular Soil Quality Test Kit.

University of Minnesota web page explaining organic matter and it’s fractions. Pretty concise, easy to read page. There are a couple minor points that I would take some issue with in this but they are minor and it’s probably just a matter of perspective/semantics.

Ed Winkle’s perspective on organic matter in his HyMark High Spots blog. Ed posts a lot of good perspective.

I would also highly recommend the text “Soil Organic Matter in Sustainable Agriculture” edited by Fred Magdoff and Ray Weil. This is my “go to” reference at the moment. A little pricey though.

I hope these references help y’all with any questions regarding SOM.

About Chuck

Soil Scientist USDA/NRCS, Owner - Soilhealth.net
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