Sorghum & Soil's Secret Life

If this post gets you excited about working with sorghum, come to one of the Carbon Sponge sorghum workshops in Brooklyn on March 9th and March 16th! They’ll be taught by some serious baking experts — Sarah Magid and Katie Phelan — whom I interviewed for my next newsletter about using sorghum flour.

Carbon Sponge’s harvested sorghum

“Microbes are the life force, the heartbeat, of the soil. They are responsible for transforming atmospheric nitrogen into plant-available form. They create the soil structure – or intricate tunnels and crevices – into which small carbon particles are buried. The list is endless, and it puts them at the center of the soil carbon sequestration story. But ultimately, our health, and the health of the earth, depends on these invisible and diverse soil microbes.”

If you’re like me, your understanding of the subterranean world might rest on some half-remembered high school classes about the carbon cycle and the general idea that decaying vegetables are good for plant beds. When you think of a garden, you picture the flowering abundance of summer, but, underneath that, just inert brown stuff. Carbon capture is a problem, of course, but it’s a problem for governments to solve, not people.

Brooke Singer came to her work on carbon sequestration (essentially, plants’ storage of carbon in soil) via the unlikely path of public art. After working on a project around food waste and then starting a community compost garden in Brooklyn, she became curious about the fact that all the soil testing kits looked for the absence of toxins (heavy metals, mostly), but not the presence of health (like its level of microbes). “It created this framework for soil to be seen as bad or something to fear, and I was wondering how we could collect other data to round out the picture of soil [as a living system].” She managed to work with scientists and put together a suite of soil tests, including one for microbial biomass, that could be used by community gardens. The idea was for gardeners to learn more about the health of their soil, but also to emphasize the ecosystem services of community gardens and show how they were helping contribute to a carbon neutral future for the city.

Her public art and education work with soil continued as the designer-in-residence for the New York Hall of Science. In raised beds outside the museum, she grew cover crops like sorghum that improve soil health. “Seeing these massive sorghum plants, they were stunning, and they stopped people in their tracks,” she said. The more she learned about sorghum, the more obsessed she became. “They have deep roots and they're drought tolerant, they’re C4 plants, which means they photosynthesize carbon a lot more efficiently, and all these things make them a climate-smart, resilient, dependable food source.” Cover crops aren’t usually counted as a cash crop, she added, but sorghum grain or sap can be harvested as food, so farmers could make a little income while they replenished their land and captured carbon from the atmosphere. She’d been talking to some farmers upstate about how they manage their soil, but small farmers are so squeezed on budget and time that it was a lower priority for them. She decided to reposition her project as an upstate hub that offers carbon farming resources. “I chose sorghum, having fallen in love with it and realizing how easy it was to grow, and it was a great starter plant for this conversation.”

Sorghum originated in Africa, and has culinary uses around the world, from the gluten-free flour jowar in India to the base for baijiu in China to the syrup that’s popular in the American South. But the grain isn’t frequently eaten in the U.S., which is why it came as a surprise to me to learn that the U.S. is the world’s largest producer of grain sorghum. The explanation for that is animal feed, which mostly gets exported to China, followed by biofuel. If sorghum is so great for the soil and carbon capture, I asked Brooke, then isn’t it good that we’re already growing so much of it? Why do you want to encourage more farmers to grow it?

Her answer was multifold, and helped me to further excavate my understanding of the inert brown stuff that I knew so little about. If you think of soil as a system, in the way that a forest is a web of relationships built over time, then it becomes clear that it isn’t about having one magic bullet plant or an optimized mix of nutrients injected into the ground. Soil is a physical structure that holds micro- and macro-organisms while cycling water and nutrients. A farmer who is managing their soil health (or Nature, who is the best farmer) is helping that system thrive by rotating crops to change up the nutrient needs and curbing erosion and soil respiration (or release of carbon) that comes from excessive tilling, among other practices. While sorghum may be a better choice than other crops, it’s still mostly planted in monoculture farms that require chemical fertilizers, herbicides, pesticides and tillage that kill off the life of the soil and release carbon back into the atmosphere.

Then there’s the human-social-economic system around these vast monoculture farms, that tend to mistreat workers as a matter of course and produce crops at a scale that require long distance shipping, while selling them at such low costs (often lower than the cost of growing them) that small farmers can never compete. With the goal of improving the soil ecosystem, it’s this human-agricultural system that Brooke hopes Carbon Sponge can target. She and her partners can take on the work and costs of developing local varieties of sorghum for growing in the northeast, for example, and build up some infrastructure around harvesting and processing its sap and grain.

The sorghum sap is how I came into the picture. A friend who reads this newsletter and lives in the area put me in touch with Brooke when her team was trying to figure out what to do with the gallons of sap they were squeezing out of the sorghum stalks. Sap is typically boiled down into sorghum syrup, similar to maple syrup, but they didn’t have the time or machines for that during the heavy harvesting season in September. I drove out to the field to taste the sap at its freshest — it was bright and sweet like sugarcane juice but also grassy with a hint of bitterness that reminded me of matcha. It was delicious drunk from a cup minutes after being squeezed, but in the fridge at home would degrade quickly into a less-nice kind of bitterness. I tried making a sorghum shrub, which uses vinegar and sugar as preservatives, but the sorghum flavor itself became overwhelmed. My favorite creation was an extremely simple sorghum sorbet — just the sap, a little more sugar, and a pinch of salt. It was delightfully green and held its grassy matcha flavor well over time.

Brooke is hoping that if more people get to know and appreciate the food that sorghum offers, we can develop a local market that makes it more attractive to grow. Through the winter, I’ve been experimenting with sorghum flour, and have come to appreciate the flavor it adds to baked goods. It also has a lot of quirks, as a gluten-free flour with a somewhat pasty texture, but my next newsletter will go more deeply into how to work with it, drawing from my experiments and the expertise of two brilliant bakers — Sarah Magid and Katie Phelan. There is so much flavor and complexity that can be added to baked goods by stepping away from all-purpose flour for literally every purpose. Plant diversity is good for the health of the land, but it’s good for ours as well. For bakers, a little grain diversity can be a jumping-off point for creativity.

I wrote my last newsletter about tracing the paths of ingredients from the land to my kitchen. Sorghum is teaching me to look into that land and see how the problems beneath it both mirror and connect to the ones above it. A low-labor crop that small farmers can rotate into their fields and that produces a nutrient-dense local grain is an exciting prospect that gets at a number of systemic issues at once. It’s still not a silver bullet — local food is still so much more expensive than industrially grown commodities — but we can start by building up these systems that enable cooks to choose products that support our farmers and land at the same time.

Bright green fresh sorghum sap

What I’m Cooking