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He hated pigeon peas. Now they could help feed Puerto Rico.
A Stanford alum is betting on a humble legume to help rebuild the island’s fragile food system—starting in backyard farms.
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Gutierrez harvesting lettuce from a field trial in the Salinas Valley, part of his research to help farmers comply with a soil nitrate reduction policy. Photo courtesy: Diego Gutierrez
As a kid growing up in Texas, Diego Gutierrez, ’25, dreaded the nights when his mom made arroz con gandules for dinner. To his mom, born and raised in Puerto Rico, the rice with pigeon peas dish was part of their family’s heritage, a way to connect her children to the island she missed. To Gutierrez, the peas were just gross.
He wouldn’t always feel that way.“It turns out that this pea that I hated growing up is actually pretty amazing,” he says. “As a scientist, I want to make food systems more sustainable and equitable, and it’s helping me do that.”
Today, the Stanford alum is working to popularize the pigeon pea as an affordable and environmentally friendly alternative to synthetic fertilizers. If successful, this planting method could help transform small-scale agriculture in Puerto Rico, providing a more efficient way to grow traditional crops for hundreds of thousands who have long struggled with food insecurity.It’s hardly an abstract problem. The island’s food system was dealt a devastating blow in 2017 when Hurricane Maria tore through. The storm destroyed plantain patches, coffee farms, and banana plantations. It wiped out cattle ranches, dairy barns, and chicken coops, as well as roads critical to Puerto Rico’s agriculture infrastructure.
Ultimately 80 percent of the island’s agricultural value had been lost. For households already reliant on imported food and nutrition assistance benefits, this wasn’t an inconvenience—it was the difference between eating and going hungry.
Cultivating change through soil science
Gutierrez never met his late paternal grandfather, who had been a farmworker in southern Texas. But learning about him through stories helped kindle his own interest in agriculture.
“I remember going to Charco, the small town where he had lived, with my parents and brother. We searched for the land where he picked cotton, melons, and other crops. Even as a young kid, I understood that his life had been really hard,” says Gutierrez.
“As I grew up, I wanted to do something to help people like him.”
Studying agricultural policy seemed a logical place to start, and that was Gutierrez’s plan when he began his frosh year at Stanford. But that fall, an Introduction to Earth Systems lecture from Claudia Avila, then a postdoctoral fellow in soil and environmental biogeochemistry, set him on a different path—one that would ultimately connect his interest in agriculture with his Puerto Rican heritage.
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Left: Gutierrez at his research site in Aibonito, Puerto Rico, taking soil samples to mail to Stanford for analysis. Right: Gutierrez taking soil samples in the Salinas Valley for Stanford's Sustainability, Engineering, and Science Undergraduate Research program. Photos courtesy: Diego Gutierrez
“She made this really interesting analogy, how soil is formed like a shaved ice cone, but she used the Spanish word raspada. For me, things just clicked because I had grown up enjoying raspadas on summer days,” he says.
“That lecture opened my eyes to soil science, a discipline I didn’t know existed. I realized that scientific research was a way to influence agricultural policy.”Diego Gutierrez, ’25
Gutierrez set his sights on an Earth systems degree, focusing on sustainable food and agriculture, and secured a spot in the university’s Sustainability, Engineering, and Science Undergraduate Research program. Through the program, he spent the summer in a campus lab and made visits to the Salinas Valley, south of San Francisco, to learn how to use cover crops to remove surplus nitrate from the valley’s soil. As nitrogen moves between the atmosphere, soil, water, and plants, it produces nitrate, which can seep into and pollute groundwater if allowed to accumulate in soil. Doctoral candidate Anna Gomes mentored Gutierrez as he developed his lab skills, encouraging him to generate his own research ideas, and it wasn’t long before he did.
In the months that followed, Gutierrez reflected on his experience in the Salinas Valley and the economic and environmental costs of using synthetic additives to increase soil nitrogen. He had learned that pigeon peas—those legumes that his mom used to make him eat—can produce nitrogen organically as they grow, and he began to wonder: Could planting them alongside other food crops eliminate the need for synthetic soil additives in Puerto Rico?
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Left: Gutierrez at his research site in Aibonito, Puerto Rico, taking soil samples to mail to Stanford for analysis. Right: Gutierrez taking soil samples in the Salinas Valley for Stanford's Sustainability, Engineering, and Science Undergraduate Research program. Photos courtesy: Diego Gutierrez
Sustainability, security, and tradition
Puerto Rico imports about 80 percent of its food supply, and roughly 40 percent of residents rely on nutrition assistance benefits. Disruptions to the supply chain—such as hurricanes—can prove disastrous. Household gardens provide space for subsistence farming, but they often require expensive imported fertilizers. A natural, affordable alternative could make home gardening more accessible and give families greater autonomy over their food, enabling them to meet their nutritional needs with crops of their choosing instead of relying on imports.
With undergraduate research funding from Stanford’s Earth Systems Program and the Office of the Vice Provost for Undergraduate Education, and mentoring from Gomes and Scott Fendorf, the Terry Huffington Professor of Earth Science, Gutierrez conducted a field trial. Using his aunt’s chicken farm in Aibonito, Puerto Rico, he tended crops of pigeon peas, cassava, and taro—staples of the traditional Puerto Rican diet. He mailed soil samples back to campus for analysis and spent hours poring over scientific literature about legumes and their nitrogen-producing abilities.
Gutierrez learned that pigeon peas can thrive even when planted alongside other crops, a practice known as intercropping. When the intercropping is done in nitrogen-depleted soil, the peas produce nitrogen that facilitates the growth of the other plants, reducing the need for chemical fertilizers.
“My research shows that farmers can incorporate pigeon peas into their agricultural systems to displace fertilizer costs, which can be barriers, and that opens up a lot of doors to growing more food on the island. In addition, this means access to food products that are culturally important and not widely grown anymore,” says Gutierrez.
From Stanford to Michigan—and beyond
Today, Gutierrez is continuing the work he began at Stanford, pursuing a master’s degree in sustainability and environmental science at the University of Michigan. With his advisor, agroecologist Ivette Perfecto, he is exploring additional ways to incorporate pigeon peas into Puerto Rican agricultural systems. He says his undergraduate experiences gave him a head start on his next research project, which will involve coffee crops.“I want to be a scientist. I want to continue learning and researching,” says Gutierrez, who plans to pursue a doctorate degree. “I didn’t know what research could be, and then I was exposed to it and was like, wow, this is a really important and impactful thing.”
A passion for scientific research isn’t the only thing Gutierrez picked up at Stanford. He’s also developed a taste for pigeon peas.
“Unfortunately, I haven’t found them in Michigan yet,” he says.
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