From the Field
Building Cover Cropping Communities of Practice in California’s Central Coast
A research team co-led by BFI Faculty Director Tim Bowles recently received a grant from USDA to evaluate the benefits of winter cover crops in the context of water quality and quantity.
In California’s Central Coast, often known as the country’s “Salad Bowl,” intensive vegetable and berry production dominates the landscape. Adoption of winter cover crops is low — as little as five percent of the farmland in this region goes to cover cropping, according to BFI Faculty Director Tim Bowles. Yet, research has shown that winter cover crops can play an essential role in protecting against nitrate pollution in California’s drinking water.
This summer, the US Department of Agriculture made an $8.1 million investment in sustainable agroecosystems through its National Institute of Food and Agriculture. As part of that investment, a team led by Tim Bowles and Hannah Waterhouse, Assistant Professor of Agroecology and Watershed Ecology at UC Santa Cruz, has been awarded a grant of $900,000 over four years to study different cover crop management practices in the context of both water quantity and quality. The research team also plans to form a “community of practice” among farmers and technical assistant providers to test these cover crop systems on working farms.
Cover crops like grasses and legumes are not intended for harvest. Rather, farmers plant them between cycles of cash crops as a way to keep the soil healthy. In the context of California’s Central Coast, where the use of synthetic fertilizers has caused a pervasive pollution problem, these plants can hold excess nitrate in place in the soil and prevent it from entering the groundwater during winter rains.
This preventative solution to nitrate pollution can be especially beneficial near small, unincorporated communities — often home to the region’s predominantly Latinx farmworkers — that don’t have the financial resources to treat drinking water or drill wells deep enough to reach below nitrate contamination.
Even as cover crops protect water quality, growers in the Central Coast often do not choose to implement them into their rotation. One of the reasons for this: water scarcity. Establishing cover crops often requires irrigation water in a region where water is scarce and expensive. In the Central Coast, 95 percent of irrigation water comes from groundwater basins that have been critically overdrafted.
The team’s research is aimed at this concern — “The simplest way to think about it is: A large cover crop might take up more nitrate but use more water, so how can you optimize both protecting water quality and minimizing the consumption of water by cover crops?” says Bowles. “We’re trying to find the balance.”
Led by PhD student Miguel Ochoa, the team planted cover crops on Gill Tract to test how different mixes of grass and legumes perform.
Over the next three winters, the team will work at the UC Santa Cruz Center for Agroecology research farm to explore cover crop management options to identify systems that best protect water quality while reducing the water consumption tradeoff.
Much of the work at the research farm will be led by Miguel Ochoa, a PhD student in the Berkeley Agroecology Lab led by Bowles. Following field trials at UC Berkeley’s Gill Tract in Albany, Ochoa plans to test out a variety of grass and legume mixes, using sensors to measure soil moisture. Ochoa also explains how planting and termination timing also factors into the trials: “If you plant an October crop, it’ll grow faster and preserve more nitrogen in the soil, but it’ll also use way more water. In a drought environment that might not be something you necessarily want,” he says.
Ultimately, the research team aims to reduce some of the barriers to cover cropping, especially among the small- to mid-scale farmers who are motivated to implement cover crops yet don’t have the resources to do so. “Farmers know that cover cropping is a good idea,” says Ochoa, who grew up in East Salinas and explains that many of the farmers in his hometown face some of the highest land rents and water prices in the country, which often pushes them to invest in speciality crops or work for larger farms.
To support these farmers, the research team is partnering with Sacha Lozano of the Resource Conservation District of Santa Cruz County and Aysha Peterson of the Resource Conservation District of Monterey County to build what the team is calling a “community of practice.”
This community will comprise up to 30 farms, where Bowles, Waterhouse, and Ochoa will work with the growers to test farmer-selected cover crop management practices to understand how these crops behave in a variety of soils, climates, and topography. “We’re providing support for these farmers to share experiences and potentially equipment with each other,” says Bowles.
“Ultimately, that’s how we’ll change things,” says Ochoa, “by building a community of practice around farmers’ needs.”