A Humble Truth About Soil Carbon

 

It's a strange time to be young. We Spoon Full farmers are looking toward a future world that may be barely habitable, for our future children. We want to do something to help stabilize this planet's climate, and while we're at it, take better care of our fresh water and the birds and bees who keep us alive. That's a big part of why we farm, and the key to our decisions about how we farm.

The industrial meat system gets a bad rap from environmentalists, and deservedly so. Yet, as often happens in complex discussions, the public discourse about meat production misses crucial subtleties. Because confined, grain-fed livestock systems create so many egregious public and environmental health problems, some people say we must stop raising farm animals altogether. If you're reading this piece, though, you may have heard that pasture-based grazing systems can produce lots of food while boosting biodiversity and soil health (and, accordingly, water and atmospheric health). Perhaps you've heard of "Carbon Farming," or regenerative grazing, or holistic management. Perhaps you've seen Spoon Full Farm.

If you have, you've probably heard us talk about how our cows build soil, and we have probably pointed out the clover volunteering in our pasture, and maybe even the young elderberry growing up along the fenceline. Maybe you've seen, smelled, or heard the vitality growing in the fields. We certainly have; here, and on other farms, too. Anecdotal evidence abounds, for the soil-building, vitalizing effects of regenerative grazing. What's harder to find, and in some ways more important, is numerical data.

The theory behind this grazing system (it has many names and varieties: regenerative, rotational, management-intensive, and holistic grazing, to name a few) is based on biomimicry: grasslands evolved with ruminant animals, who migrated and fled from predators such as wolves and humans. Over time, such migratory grazing, manure-dropping, and trampling builds deep, rich soil, like the soil that has defined the "bread basket" of the American midwest. So modern graziers are moving cattle quickly around their miniature prairies, and watching the soil grow, while producing abundant protein for humans. That deep soil, of course, holds lots and lots (and lots - soils represent a huge, accessible "carbon bank" into which we can make deposits, out of the air) of carbon. A lot of CO2 has been released into the atmosphere by soil-degrading agricultural practices such as tillage. If we can put some of that carbon back in the ground, we could potentially stabilize Earth's climate.

"Cows save the planet?? That's a beautiful story. But it seems too good to be true," you might say. "Prove it."

Numerical data can -and should- affect individual choices about what to eat, investment choices about which farm systems to adopt, and societal choices about what to subsidize and support. So before we grow too enthusiastic about regenerative grazing, we need to see the numbers.

Now, in Summer 2019, some data has come in, and more is on the way. Let's look at three examples.

Marin Carbon Project - Organic Matter Stimulus

On gorgeous pastures in Northern California, several ranchers and scientists are collaborating to test how various different techniques of ranch management affect carbon in the soil. For this post, let's focus on one particular experiment, which looked at soil carbon and compost.

In a 2013 study, soil scientists applied 1.3 cm of compost across two fields. This mimics a practice that many graziers use during late spring or fall: spreading composted manure from cattle that lived in a barn over the winter. The scientists then measured soil carbon using soil samples, and soil respiration (how much CO2 did soil microbes breathe out), at frequent, regular intervals. The results were amazing: soil carbon in the composted fields increased 25-70% annually, beyond the amount of carbon that was applied in the beginning of the experiment (compost has lots of carbon).

It seems that a one-time application of compost, with its combination of carbon, nitrogen, and microbes, stimulates soil to store more carbon. It's like a push that starts a snowball rolling downhill.

So this particular study shows that one particular aspect of regenerative grazing may, indeed, stimulate soil carbon storage. But it doesn't address other fundamental regenerative practices, such as "intensive grazing." Luckily, some data about that practice has recently been released, from a ranch called White Oak Pastures, in Georgia.

White Oak Pastures - Regenerative Beef Lifecycle Analysis

White Oak Pastures is a large, venerable operation that raises pretty much every livestock animal you can think of (cows, chickens, sheep, hogs, rabbits, ducks, goats, llamas... and more). Recently, they partnered with a well-reputed sustainability analysis firm called Quantis, to measure the carbon storage in their soils. You can read over a preliminary summary of the study, which is still being peer-reviewed (a long process!), here.

Based on careful soil sampling, Quantis found that White Oak Pastures' grazing system stored 35 kilograms of carbon in the soil, for every kilogram of beef produced, net. (This accounts for the various emissions that occur during beef production, such as slaughter, transport, and enteric emissions - methane* - burped out by ruminant animals such as cattle.) These 35 kilograms of carbon are equivalent to the emissions of an average passenger car driving about 87 miles. That means, if 20% of the ~50 billion pounds of beef (notice that assumptions about beef’s impacts, in that NPR article, refer to beef raised in an industrial corn-fed system) eaten in the United States annually were raised in a regenerative system, our carbon emissions reduction would be the same as driving eight hundred and seventy billion fewer miles (out of 3.22 trillion miles driven, total).

This is, simply put, pretty incredible. As the summary shows, even reputedly sustainable food like soybeans emit net carbon dioxide, rather than reducing atmospheric carbon dioxide. White Oak's grazing practices, on the other hand, reduce atmospheric carbon - even when, Quantis researchers note, their extrapolations about how much total carbon is stored are conservative (read: underestimates), and their assumptions about enteric methane emissions from cattle are liberal (read: overestimates)*. So the scientists are being careful, and their minds are still being blown.

Whoa. We need to test that, again. While we're at it, let's test that Marin Carbon Project study about compost again, together. Let's do it at Spoon Full Farm.

Spoon Full Farm - Effects of Compost And Intensive Grazing on Soil Carbon

Marin and South Georgia are very different places from Spoon Full Farm. We're hot and dry in the summer, and bitter cold in the winter. Our soils are quite sandy. All of that is good - it means that our farm offers another test: will the farming techniques described above lead to similar soil carbon sequestration, in this different climate and soil type?  

We started intensively grazing in Fall, 2017, after the pastures here at the farm had been "conventionally" hayed, using synthetic nitrogen and Monsanto RoundUp, for decades. We are fortunate to have baseline soil carbon measurements, from the very beginning of our project, so we can watch the land change.

Now, in collaboration with Professor Carey Gazis from Central Washington University (just 14 miles east of Spoon Full Farm), we are analyzing soil carbon annually, on several sites across the farm. In the garden, where we amend with compost and grow a diverse variety of plants, copious carbon is being stored deep in the soil. 

On the other hand, our pastures are anemic. In withdrawals after so much synthetic fertilization and, in theory, offering huge potential for accumulating and storing carbon. So we are testing the compost application technique demonstrated by the Marin Carbon Project. This fall, we will apply a .42-centimeter layer of compost to 37 acres of pasture, while we also test the effects of our rotational grazing system. This is made possible by a grant from Tilth Alliance and Humanlinks Foundation (LINKS); we tip our hats to those organizations. 

Humus and Humility

As much as these soil-carbon data excite us, they also remind us to be humble. 

We recognize that there are still enormous uncertainties about the effectiveness of regenerative grazing, when it comes to carbon storage. It will take decades to fully understand what role these techniques can play in the carbon cycle. Our instincts tell us that regenerative grazing will be a relatively small but critically-important part of the future of humanity's protein production and consumption. 20%, 30%... we don't yet know exactly how much of the industrial meat system should be replaced by regenerative grazing, and how much should be replaced by meat alternatives, insects, or (many of us shudder to think) lab-grown "meat." 

We also recognize that the truest ecological benefit of these practices takes place underground. There, invisible microbes, grass roots, and worms collaborate with the cattle and chickens to build humus. Humus is the organic (read: living (or dead, which means formerly living)) portion of soil. Humus offers food, water, shelter, and air to crops. Where there is humus, much less fertilizer is needed for high production, viral and fungal pathogens are less threatening, and water is stored and deployed with great efficiency. High humus content correlates with high soil-carbon content. 

The word Humus is the latin root for our word 'humility.' A humble attitude seeks to serve, without needing visibility or recognition. Good soil, then, is literally humble, in multiple ways. 

So if you, too, are concerned about the future of the biosphere, you have several options for action. You may buy an electric car or put solar panels on your house. You may take to the streets for a climate march, and vote for representatives who take earth-care seriously. at the same time, you can take a humble approach: you can get to know the soil where your food grows. You don’t need to eat meat (many vegetable production systems can also store carbon, especially without tillage), you’ll just need to make sure that your farmers are humble enough to help the soil quietly store carbon, while producing the food you eat every day. Cultivating the humility to know the soil that your life depends on will nurture your body, your imagination, and the earth.


*An aside: Regarding Methane

Many commentators, including the scientists who conducted the White Oak Pastures study, blame burping cows for various degrees of Greenhouse Gas emissions. It is true that rumination, the digestive process of breaking down grass into protein, produces methane as a byproduct. Methane is a short-lived Greenhouse Gas that is 100x more potent than carbon dioxide. We consider this issue often, and invite you to consider three reasons not to point the finger at cattle, alone:

  1. First, the number of ruminant animals on this planet has not actually changed that much over the past 200 years, while the planet's warming has accelerated. Yes, there are more cattle now, and perhaps more sheep, but there are also up to 100 million fewer bison in North America. Add several million elk and caribou onto that, and then factor in the great herds of Africa and Asia, which have undoubtedly diminished, and you have a number quite similar to the current cattle population. (This is not, in itself, a justification for raising more cattle. It just shows that rising methane emissions and temperature can't be accounted for by cattle.) 

  2. Second, there are promising ways to reduce methane emissions from cattle. One way is to feed cattle some kelp (which we do at Spoon Full Farm, because it offers myriad other benefits for animal health). Another is a Swiss feed supplement called Mootral. It promises to reduce methane burps by 30%. 

  3. Third, and perhaps most importantly: Synthetic fertilizers and fossil fuels seem to be the real methane culprits. Fracking natural gas is a major, growing source of emissions. So, too, it turns out, is synthetic nitrogen production. This study from Cornell shows that fertilizer factories in the USA seem to emit over 100x more methane than they had self-reported, emitting more than all the rest of USA industries combined. 

  4. If corroborated by further study (and not suppressed by the large fertilizer industry), the above study about synthetic nitrogen represents one of the biggest, least-talked about environmental stories of 2019. Most conventional food production systems, including the corn and soy used for both industrial meat and for meat alternatives, rely on synthetic nitrogen. That means that the emission impacts of such vegetarian systems are drastically higher than most people think. It means that we must reconsider how we produce lots of food, or learn how to utilize nitrogen in dramatically different ways. Here's that study link, again: https://news.cornell.edu/stories/2019/06/industrial-methane-emissions-are-underreported-study-finds

 
Mericos Rhodes