I’ve been talking a lot about glomalin lately on social media and I thought it might be helpful to describe exactly what glomalin is and why it’s important. They say it takes 1000 years to make an inch of topsoil, and that topsoil is perhaps the most valuable substance on the planet. Plants rely on topsoil to grow the food that we eat. Even meat is dependent on the growth of the plants that the animals eat. So what makes topsoil so incredible? More importantly, what makes it different from other kinds of soil? The difference is the presence of stable soil carbon. That carbon is incredibly powerful in small amounts as the best topsoils only have around 5% carbon, with most containing under 3%. That carbon is enough to drive the biological processes necessary to create healthy ecosystems, cycle nutrients into a form that’s biologically available for plants, and create an immune system that drives the health of the entire ecosystem.
So what makes up that soil carbon? Okay, maybe that’s too big of a topic. Let’s just talk about the single largest portion: glomalin. It was once thought that humic acids make up the largest constituent of soil carbon, but as we learned how to test for glomalin and that testing became more prevalent, we learned that humic acids are more like 8% of the stable soil carbon, while glomalin can be up to 30%. So what does that glomalin do?
Glomalin is a protein (technically a glycoprotein, a protein attached to a sugar, but I digress…) that acts primarily as a soil glue, gluing soil particles together to make aggregates that benefit the soil structure, help soil retain water, and reduce erosion. This soil structure is ideal for fostering the conditions for soil organisms and allowing plant roots to grow. But that’s not all glomalin does. Glomalin plays a part in the cycling of nitrogen into a form that is usable by plants, thereby increasing the bioavailable nitrogen in the soil. It also binds to heavy metals, making them unavailable to soil biology.
There is another function of glomalin that is of particular interest globally. Glomalin is defined by its toughness. We didn’t discover it until 1996 when Dr. Sara Wright discovered that you can separate it from the soil particles it is bound to by soaking it in citrate and then autoclaving it at 250 degrees F repeatedly until it releases. In fact, as we learn more about it, it’s become apparent that it’s more a family of proteins than a single protein, and the term Glomalin-Related Soil Protein (GRSP) has cropped up. But lately, it’s become apparent that it’s even more appropriate to define it by the extreme measures it takes to isolate it, calling it ACE (Autoclaved Citrate Extractible) proteins. It’s this very toughness that makes glomalin interesting. It can take 40 years or more to break down in the soil under normal conditions. This makes it ideal for sequestering carbon. In fact, as various organizations talk about sequestering carbon in the soil, they are mostly talking about glomalin. Glomalin is officially classified in carbon sequestration circles as a medium-term carbon sequestration method.
Where does glomalin come from? I’ve talked before about mycorrhizal fungi, but in summation, mycorrhizal fungi are a family of soil fungus that forms symbiotic associations with most plants. The fungus goes out into the soil and gathers nutrients and water and delivers it to the plants. In exchange, the plants give the fungus sugars that they use to meet their metabolic needs. This exchange happens at the microscopic level on the tiny root tips of the plants. There are many types of mycorrhizal fungi, and one of those is arbuscular mycorrhizal fungi, many of which are in the genus Glomus. For this type of mycorrhizal fungus, the exchange happens at the surface of the root, an environment that is very active with various soil organisms. The fungus secretes the glomalin to sort of glue the connection shut and minimize loss of valuable sugars and nutrients. The fungus also seems to use the glomalin to boost the strength of the fungal fibers, called hyphae, that it uses to transport nutrients in water. In effect, it uses the glomalin as a stiffening agent to create the pipe network it uses to get the nutrients to the plants.
The soil structure is an alive, active environment. Those root tips last an average of 4 days before the root grows on or abandons that root tip to grow elsewhere. Likewise, the pipe network is constantly being rebuilt and rerouted. Honestly, there is a significant parallel to single-use plastics here. A compound is created that is used for only 4 days but takes 40 years to break down. The big difference, of course, is that the glomalin is amazingly beneficial in the soil whereas plastics are not. But just like those plastics in our environment, the glomalin builds up in the soil, which is what makes it the most prevalent form of soil carbon I mentioned above.
When we till land to engage in industrial agriculture, we destroy the living organisms who inhabit that soil, and they become fertilizer as they decompose. As a soil becomes more degraded and the soil carbon is lost, we have to add fertilizer to keep the soil productive. But the fertilizer we add doesn’t directly feed the plants like we think it does. Instead, it activates an increasingly small population of soil bacteria and helps them burn through increasingly small soil carbon content to provide the fertility we need. It’s all a bit more complicated than that, but that’s the gist. In a nutshell, industrial agriculture is a mining operation that feeds humanity by mining carbon out of the soil. The thing is, this whole process is massively unsustainable. In 2014, the Food and Agriculture Office (FAO) of the United Nations came out with a report that stated that if we continued current agriculture practices, we would only have 60 years of agriculture left before we can no longer feed humanity. Of the various components of soil carbon, glomalin is not only the single largest constituent, but also the most resistant to decomposition. Again, the issues are complicated, but it wouldn’t be too far off to say that we are currently feeding 8 billion human beings largely through the process of mining glomalin out of the soil.
That begs the question: is glomalin a renewable resource? It is made through the activity of healthy ecosystems. We know how to create the conditions that make glomalin. The problem is, heavily degraded soils can take years to repair to the point where they start making glomalin. When the process is started back up, it can take decades for the glomalin to build back up in the soil. There is one study out of Brazil that asserted that if you want to tell how degraded a soil is, all you have to do is measure the glomalin. Highly degraded agricultural soils can have a glomalin content of well under 0.1%. A typical amount for healthy soil that is high in organic content will be in the range of 0.6 to 0.7%. One study that took samples from ecosystems all over the State of California came up with a highest reading of 4.5%. There have been a few samples, most notably from Maui, that measure 10%, but even the 4.5% is an outlier.
Since glomalin was first discovered so recently, there are, unfortunately, relatively few people who are aware of its existence or its importance. There are only a handful of studies out there that have really dug in to study what all it does. One of the common threads in those studies is lamenting the fact that, because of the way glomalin is produced, there’s no way to produce exogenous (made in one place and applied elsewhere) glomalin. Not only does it limit the use of this amazing compound, but it also make studying it more difficult. There may be so much more that this amazing compound does.
So why does a company that focuses on raised bed gardens have an interest in glomalin? As I’ve mentioned before, a LEHR Garden produces a rich compost as an output. That compost is made while plants grow in it. We inoculate those plants with arbuscular mycorrhizal fungi. We recently found a lab that can test for the presence of glomalin, called an ACE protein test. Our sample tested at 6.5% glomalin.