Gold Underfoot! Soil Organic Matter matters—Raffa Sindoni

Soil is the tapestry upon which all life is weaved. Our water is cleaned through it. Our food rises from it. As young children, our bare feet kiss it. After death, we return back to it.

And so, the cycle goes, for time immemorial.

Most splendid of all, a full-spectrum of life flourishes in just one tablespoon of soil. At first, we’re taught that soil is just a mishmash of rocks. There is some truth there, of course, but mineral particles and geologic decay are just one small part of the story – the rest is quite literally alive. This alive, decaying, and/or organic portion of our soil is called Soil Organic Matter (SOM) and holds the key to the sustained future of humanity, our environment’s regeneration, and the resilience of our global climate.

What is SOM?

SOM is any material originally produced by a living organism (plant or animal) that is now decomposing in the earth – leaves, wood, roots, animal flesh, fruit, and bone, just to name a few. SOM is 58% carbon, most of which is pulled in from the atmosphere and digested by microorganisms that live in the soil and become accessible to plants again. Storing atmospheric carbon into the soil may not only reduce the overall load of greenhouse gasses, but it is also excellent for overall soil health.

SOM also includes the microscopic organisms that decompose these organic bits, which then go on to become nutrients and soil substrate. This bundle of living and decaying matter, which we call SOM, is in constant relation with those mineral particles (e.g. sand, clay, silt), as well as the water and air that exist below-ground. This is the rich story of our soil ecosystems.

A picture containing diagram

Description automatically generated

SOM is a cocktail of decay, life, and reciprocity. It is the engine for new plant growth. It ensures that soil can retain water for plant uptake, facilitates nutrient transfer to plants, and stores atmospheric carbon below the ground. Yet, not all soils contain the same amount of SOM. Some soils are naturally richer in organic matter than others. For example, forest soils naturally exhibit higher levels of organic matter than desert soils because of greater water availability, higher biomass of plant matter, and more temperate climates.

A Call to Investigate – SOM in the West

However, SOM differences across the U.S. may not only be attributed to natural variances in climate, plants, and soil types. Our society’s industrial advancement has stripped away organic matter from our soils at alarming rates by disturbing earth’s natural cycles. Centuries of monocropped agriculture, changes in grazing intensity, and urbanization have expanded without much consideration of holistic soil health and results in lesser SOM across the U.S. 

In the West, rapid urban sprawl in places like Bozeman, MT threatens SOM stocks by building impermeable surfaces, like roads, home foundations, and more. As illustrated by Soils Revealed, which measures historical changes of Soil Organic Carbon (a direct correlate to SOM), many pockets around the West have experienced historical declines of organic matter (in gray rectangles below), which include Oregon and Washington east of the cascades, areas surrounding Bozeman, MT, and all throughout South and East Wyoming. There is a deep need to understand exactly what is driving this loss of SOM across the West – whether it is urbanization, unsustainable ranching or agriculture, a rapidly changing climate, or some interaction of these factors together.


Description automatically generated

Figure 2: Soil Organic Carbon (SOM) Losses in the West (Source: Soils Revealed)

Weather-Proofed Soils

As we consider how humanity can better live in reciprocity with our soils, we must focus on the importance of soils to our own wellbeing. As we face the impacts of climate change, we must ensure that our food systems can withstand droughts and extreme heat. If we work to increase SOM, we can actually weather-proof our soils against climate change, so that they may keep cleaning our waters, growing our food, and de-carbonizing our atmosphere. In one example, soil experts from Yale demonstrated a clear link between crop drought resiliency and the abundance of SOM (see figure 3 below). SOM is the golden ticket, and land managers should consider stewarding their land to maximize SOM like their lives depend on it.

Graphical user interface, chart, scatter chart

Description automatically generated

Figure 3: SOM and Crop Resiliency Against Droughts (Source: Daniel A Kane et al 2021 Environ. Res. Lett. 16 044018)

Strategies for Building SOM

In the West, land managers can work at both small and large scales to build SOM without necessarily slowing down their economic prospects. Scalable practices like regenerative farming and ranching are excellent for maintaining and improving soil health and have already become widespread across the American West. While there are some hurdles to breaking into regenerative farming or ranching, such as a possible initial dip in crop yields or increased logistical challenges from rotational grazing, prioritizing regenerative practices supports long-term land health, raises healthier livestock, and increases farm overall profit. On many occasions, consumers are even willing to pay a premium for regenerative foods

Further, rapidly developing carbon offsetting markets are in their early stages and may soon begin to pay land managers to build up SOM on their land through regenerative practices.

At a more individualized level, backyard composting and chop-and-drop gardening or landscaping is an excellent way to boost SOM in your neighborhood, all while cutting down household reliance on nurseries or hardware stores for fertilizers or soil amendments.

To see how soil in your state may change through regenerative land management practices, you can visit the Soils Revealed tool here. For example, the snapshot below shows how Soil Organic Carbon (or SOM) in California’s agriculture basin will boost dramatically if land managers increase their organic inputs and reduce their tilling usage.

If we can tap into a deeper mindfulness about fitting our human systems into the lived environment, we may be able to keep our soil healthy enough to weather droughts of the future, keep our agricultural systems producing food for generations to come, and even lessen the most severe impacts of severe climate change.