On a recent Monday, Adam McCurdy observed a lush row of cover crops at Coastal Roots Farm in Encinitas.
The cover crops, such as clover, alfalfa or barley, feed the soil, said McCurdy, the nonprofit’s director of farm production and distribution.
Farmers at Coastal Roots use cover crops and minimum tillage practices to help restore the soil’s health, reduce waste and conserve water. Healthy soil means healthy plants.
But what many farmers who use regenerative practices can’t easily do is directly restore the soil biodiversity. That’s something farmers “can’t focus on because you can’t see the number of microorganisms in the soil or what they’re doing,” said Kristin Barbour. She’s a researcher at UC San Diego’s newly launched Soil Health Center at Scripps Institution of Oceanography.
Researchers with the new center are helping farmers like McCurdy feed the soil in measurable ways. They’re developing a probiotic that could give plants the microbes they need to grow healthier and stronger.
If it works, they hope to help farmers rely less on chemical fertilizers and preserve microbiomes in soil. It’s like replacing human supplements with whole foods, like yogurt or fermented vegetables.
Soil inoculation, or adding microbes to soil, has been studied for many years. But not enough has been studied about how the interactions between soil microbes “can lead to particular outcomes,” said Sarah Allard, who directs the Soil Health Center.
“We're really interested in understanding more about that plant-microbe interaction and how we can potentially boost the microbes or even add additional microbes that can point the plants in a direction that is beneficial for food security and climate resilience,” said Allard.
Microbes are teeny-tiny organisms that support plants in many ways. They can influence which and how many nutrients plants can take from the soil and even help them resist stress, like drought or diseases, according to the U.S. Dept of Energy.
Barbour said their findings will hopefully identify specific microbes needed to enhance plant growth.
To get there, researchers are experimenting with lettuce plants at a Salk Institute Research greenhouse. One is the control group, and the other has received a few drops of the probiotic that resembles lemonade — a mixture of bacteria and fungi.
Before they can put on their lab coats and examine the plants’ microbiome, Barbour said they’re spending time at the greenhouse and at Coastal Roots Farm, taking biomass measurements, or tracking how tall each plant grows, and counting its leaves.
“For microbes, it’s a lot harder because we can’t actually see them,” she said. “We have to go through kind of a longer process where we extract the DNA to actually understand who’s there, what their abundance is within that community, and what they’re actually doing.”
Barbour said they’re also thinking about the practical ways farmers would be able to apply the probiotic.
“Right now, we can just apply it in its liquid form,” she said. “But something that might be more shelf stable might be something like a dried powder.”
Besides growing healthier food, Allard said there are several other benefits to improving soil health. For one, the stronger the root is, the more carbon dioxide the soil can store, which would otherwise remain in the atmosphere as a greenhouse gas. Industrial agricultural practices, including the use of synthetic fertilizers, release carbon into the atmosphere. One study estimated that 50-70% of carbon from the world’s cultivated soil has likely ended up in the atmosphere as carbon dioxide.
“It's also important for our food security, for our resilience to climate change, to have really robust soils that can be resilient across all the challenges that they face,” said Allard.
Researchers said they’re interviewing more farmers in San Diego County to better understand how, together, they can support healthy food production.
