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Soil Organic Matter and the Carbon Solution

Sponsored by Heliae® Agriculture

Is your soil capable of high productivity: nutrient cycling, water holding capacity and devoid of the compaction that impedes plant root performance? Does your soil host a living, thriving and diverse microbial community? Is it sticky…can it withstand rainfall events while holding the water and air your crop needs to flourish?

If not, what is missing and where can you begin making changes to put the “pieces” back into your soil productivity puzzle? Often, the answer to balancing your soil productivity puzzle starts with knowing how much of your soil’s carbon is working for you.

Hand holding soil

Soil organic matter (SOM) is the foundation of both plant and soil health and is thought to be one of the most valuable tools in capturing and storing atmospheric carbon. Made up of three distinct components, SOM can be grouped into the categories of: Living, Active and Stable, with subcategories more clearly defining the role of each within the soil biome.

We will start at the bottom, to discuss what we cannot change, first. Stable and resistant organic matter represents 60-90% of your soil test SOM%; it is the oldest, and hence most stable, organic matter in your soil’s composition. It has been chemically modified by microbes and is the result of microbial metabolization. Stable organic matter, also known as humus, is where soils derive their deep black color and can be an indicator of overall soil health and stability. Building stable organic matter is not a fast process and can take decades, sometimes centuries, a sobering thought for agriculturalists working to increase SOM.

Fortunately, labile carbon, the category of SOM that turns over the fastest and contributes the most to readily available plant nutrition, is something that we can influence. Also known as active organic matter, this SOM is made up of plant root exudates, currently decaying plant material, animal and insect excrement and other decaying organisms. Because this soil carbon is actively breaking-down, it is releasing materials that will cycle through the soil.

All soil organic matter continually cycles between living, active and stable, and around 90% of the organic carbon that enters the soil as residue will be digested by microorganisms—this sentence is the actionable take-away from this article.

You can change and manage the residue available to the microbial population in your soil, and you can influence the microbial population in your soil by adding the super food microorganisms need to populate, grow, and flourish.

Active carbon is very sensitive to changes in soil carbon inputs and farm management practices; so management practices that add active organic material to the soil can incorporate deliberate additions of labile microbial food sources. Among these food sources, microalgae incorporation has proven to be an important facilitator in the establishment and health of microbial populations and organic matter building programs. 

To better understand the productivity potential of your soil, choosing the right soil test is important. Today, there are soil tests available that focus on microbial available organic carbon and nitrogen. If you are incorporating and managing residue, these numbers and—more importantly—ratios are imperative for the breakdown of residue and the subsequent nutrient cycling that occurs. In other words, C:N ratios keep your soils covered and protected and influence the release of nutrients when you need them for a growing crop. Keep in mind that a relative constant in soil biology is a C:N ratio of 10:1, that is 10 parts carbon to one-part nitrogen, and when that balance is disrupted, either by addition or deletion, residue breakdown and nutrient cycling will be affected.

Testing that provides “right-now” as well as more static measurements, such as the Haney Soil Health Test and Cornell Soil Health Assessment, are becoming more popular as agriculture, as a whole, learns more about the soil microbiome and how the biological interactions that occur within it affect soil productivity. Both tests help producers to pinpoint and cultivate soil microbial activity—the cornerstone of healthy and productive soils.

To help producers understand microbial-enhanced soil performance, companies, and thought-leaders, alike, have invested time and resources in developing producer-focused educational opportunities. While these events vary in scope and delivery, they provide producers with the robust regenerative agriculture “tool-kit” they need to understand the productivity potential of their soils. To learn more about and register for free upcoming soil health education opportunities, with a focus on the incorporation of microalgae, visit: https://heliaeglobal.com/regenerative-agriculture/