22.8: A Case Study, City Slicker Farms

Oakland, California

When City Slicker Farms moved into its new location in West Oakland, a 1.4-acre site that was once a paint factory, the nonprofit urban farm faced the challenge of rebuilding the soil from the ground up.

While the soil went through a remediation process, City Slicker still needed to bring in new soil for the entire site. “Because this is topsoil that’s coming in and it’s being brought in big loads, the soil structure was very poor,” says Julie Pavuk, director of urban garden education. It appears that the soil also came from different sources, she adds, as soil textures vary throughout the farm.

Dealing with a new soil wasn’t unfamiliar to the organization, whose mission has been to empower community members to meet the basic need for healthy food by creating organic, sustainable and high-yield urban and backyard farms. Since its founding in 2001, City Slicker Farms has built more than 300 community and backyard gardens out of raised planter boxes. The reason they use raised beds is two-fold: community members who may not be physically able to do in-ground gardening can still participate, and they can install gardens in places where there may not be natural soil, such as parking lots. Over the years, they discovered that not all soil is fit for raised bed production. At times they had to shovel soil back out because it was too compacted, Pavuk says. It took some time to determine that a sandy loam soil called “Local Hero Veggie Mix” from a local company, American Soil and Stone, was the best fit for their planter boxes because of its structure and nutrients.

The main issue they had to address at their new location, the West Oakland Farm Park, was soil compaction. “Some of the initial challenges were just literally being able to dig in and create enough space so that the plant roots could actually grow and go down as far as they needed to be to avoid becoming stunted,” Pavuk says. To prepare the soil for production, City Slicker Farms implemented the biointensive methods of double-digging and layering in a lot of compost—residential green waste provided by Waste Management. The manual labor paid off. “Those methods really work to help us address some of those things like soil structure and make sure we’re adding a lot of nutrients back into the soil,” she says. “Just yesterday, I was out digging in some of the beds, and I was surprised at how easy it was compared to how it had been in that particular space earlier.”

Rebuilding soil was also a better challenge to deal with than the one they faced before: land impermanence. Before purchasing the brownfield that would become the Farm Park, thanks to a $4 million grant from California’s Proposition 84, City Slicker Farms operated on empty sites through temporary arrangements. They were at risk of losing their spaces at any time. Pavuk recalls one day they got the news they had one week to move out from one of their sites. “We salvaged what we could from it, and the food was distributed, but we lost one of our big production spaces, and it happened very quickly,” she says. This made the organization even more aware of the food insecurity the neighborhood faced and kicked off the process of owning their own space.

Designed in partnership with the community, the West Oakland Farm Park is not only an urban farm but also a much-needed green space and community hub where people can visit to relax, learn and play. It features a greenhouse, nursery, orchard, vegetable and herb gardens that the Farm Park staff and volunteers use for food production, a chicken coop, beehives, a demonstration kitchen, an outdoor classroom, a playground, and 28 plots for community members to garden themselves. Like the backyard gardens, the community plots have raised planter boxes to make gardening more accessible to the community, while the rest of the crop production is in-ground.

City Slicker Farms moved into the site in 2016, and it opened to the public that summer. All of the food grown at the Farm Park goes to community members who lack access to healthy food or are experiencing food insecurity. While the farm has been providing food to those participating in their gardens program, they are moving to a “community fridge” model. They’ll distribute their food through free refrigerators that an organization called Town Fridge has set up in public spaces around Oakland, allowing anyone to access free food and drinks anytime.

With a better soil structure now in place, the farm is moving away from biointensive methods and is now looking at how they can correct deficiencies to grow even healthier and more nutrient-dense foods. Farm manager Eric Telmer started with soil testing to create a fertilization plan to address some of their plants’ stunting and yellowing. He found that the soil is low in calcium and sulfur but very high in magnesium and potassium. To bring the soil into balance, he’s been applying an oyster shell flour as a substitute for hi-cal lime, as well as gypsum and CalPhos.

They rely on composting and cover crops for nitrogen. Their compost comes from three sources: compost created onsite from crop residue, such as faba bean cover crops and other organic matter sources, which they usually layer with either manure from their chicken coops or with donated horse manure; worm castings from their worm bins, where they feed the worms food scraps and burlap; and city compost. To kill weed seeds and pathogenic organisms, City Slicker does hot composting. The middle of the compost pile needs to reach at least 130°F for a certain number of days, depending on how big the compost pile is, and they turn it to ensure every part of the pile reaches the center.

For cover cropping, faba beans are the farm’s first choice because of their ability to produce nitrogen and to grow quickly. The farm will cut the beans just below the soil level after they’ve flowered but before they’ve set seed. This kills the plant while leaving the roots and nodules to continue providing nitrogen. The tops are then either used as mulch, added to compost or served as feed in their chicken coop.

The faba beans also add diversity to their rotation. While the Farm Park grows a variety of crops, including tomatoes, cucumbers, squashes, peppers, beans, radishes, eggplants, bok choy, carrots and peas, its rotation is heavy in brassicas like collard greens, mustards, kale and swiss chard. The faba beans appear to be helping to control pest issues on the brassicas, particularly aphids. Pavuk explains that the aphids will attack the faba beans, but soon after, ladybugs will appear and eat those aphids. This cycle helps keep these beneficial insects in the Farm Park to deal with aphids on brassicas and elsewhere.

Since the West Oakland Farm Park is located in an industrial area, there weren’t a lot of plant communities that attracted beneficial insects. To address that, City Slicker built insectary strips filled with plants like chamomile and bachelor buttons at the headrows of their beds to serve as a “beneficial insect oasis,” Pavuk says. “We’re looking to hopefully prevent some of our pest problems by growing much healthier plants and by increasing the amount of habitat we have for our beneficial insects, so that we’ll be able to use more of those biological controls as part of our pest management strategy.” The Farm Park also has its beehives to provide the dual benefit of pollination and honey production. In the four years they’ve been on the site, Pavuk has seen more native bee species and other pollinators show up, like hummingbirds and butterflies.

But one of the biggest indicators that their soil health practices have set them on the right path are earthworms, which they didn’t have when they first started production on the site. “Their presence to me is an indicator that our soil is improving, and they’re helping to improve it,” Pavuk explains. “That first year was so hard, in part because the soil needed so much work, but also we didn’t have the diversities of insects and creatures. The next year was amazing because then the other things started to come and the soil was improving; all of it was happening at the same time in concert.”

The crops that are crucial to their mission of providing healthy food to the community reflect that change. “The plants are thriving in ways they simply weren’t initially,” Pavuk says.