Here’s the Dirt on Urban Gardens: They May Be Better for Plants Than a Farm

A new study of community garden plots in the U.K. shows that the soil health far surpasses that of surrounding farmland.

(Photo: Danita Delimont/Getty Images)

Jun 2, 2014· 3 MIN READ
Willy Blackmore is TakePart’s Food editor.

I spent the last two weeks trying to buy animal shit off Craigslist. Specifically rabbit shit, which in some circles is considered the ne plus ultra of animal waste. This morning, I was finally able to get in touch with a guy out in the San Fernando Valley who raises rabbits (for what, I don’t know) on a diet of organic alfalfa pellets, grain sweetened with molasses, kitchen scraps, and extra helpings of timothy and alfalfa hay. They’re a happy bunch of bunnies, and that goes a long way toward explaining why I would pay $40 of my hard-earned cash for 60 gallons of their manure.

Alex, my rabbit connection, has already composted the waste and he's even willing to deliver it to my house, where it will be hauled up into the yard and used to fertilize my beans, peppers, eggplant, and kale and to prep the new garden bed that will soon be home to tomatoes and watermelon. If there’s any left, I’ll mound it around the base of the blackberry vine, rosebushes, and fruit trees—especially the pomegranate I recently transplanted. Doing so, according to a new study, could help make the dirt in my yard far more suitable for growing food than a conventional farm.

Our technology-enabled exchange, in which livestock raised in the San Fernando Valley will replenish the dry, dusty soil of my Highland Park yard, is a more drawn-out version of what happens on one of those vaunted sustainable farms we spend so much talking about—and used to be standard for just about any ag endeavor before the era of industrialized farming. Livestock is raised for meat, dairy, and eggs, sure, but one of the animals' major unsung roles on the farm is to keep the soil fertile, replenishing it with the nitrogen and other nutrients that the plants suck out to grow. Rabbit manure contains more nitrogen, phosphorus, potassium, calcium, and other micronutrients than any other kind of fertilizer.

In industrial farming, where nary two crops—never mind a whole array of plants and animals—are raised on a single piece of land, the farming essentially strip-mines the dirt. Whatever monocrop is planted sucks up all of the nutrients, and then chemical fertilizers—or manure purchased in bulk from a confined animal feeding operation—are used to build up the nitrogen level somewhat before next season’s planting.

It’s a system that, with the help of herbicides and pesticides, is responsible for plenty of record harvests—but to the detriment of the dirt. Now, a new study comparing the soil in urban gardens and farms in surrounding areas shows that it’s the backyard plots, not so many acres of farmland, that’s more suitable for growing food.

The study, published in the Journal of Applied Ecology in April, looked at the allotment plots—the U.K.’s version of community gardens—in Leicester, England, and compared the soil quality with what's found on farms surrounding the city. Both the organic carbon density—a general measure of soil health—and the nitrogen density in the allotment plots were higher than on nearby farms. The most depleted farmland tested had 65 percent lower organic carbon density than the city gardens. Dirt with a higher carbon content is better able to hold water, is more nutrient-rich, maintains an even temperature, and functions as a habitat for beneficial bugs and other organism. It’s the dirt you want to grow food in—and the dirt that will readily nourish whatever’s planted in it. In another sign of good soil health, the bulk density—a measure of how compact the dirt is—was lower in the urban gardens.

In a survey of the gardeners who work these allotments, some of whom have been growing food on the same plot for as long as 50 years, 95 percent said they practiced composting and 75 percent said they added manure to their soil. In doing so, they’re taking better care of the earth that’s supplying their families with tomatoes and greens to serve alongside food from the supermarket or elsewhere than the vast stretches of dirt that are tasked with feeding the world.

The report notes that some 800 million people around the world are growing food in urban areas—many of them are farming out of necessity, not as a hobby. The authors conclude that drawing from the management practiced by the allotment gardeners could help make those gardening for fun and those gardening to survive both reap better harvests and become part of the fabric of more sustainable cities—especially if municipalities can feed urban soil with their own waste. It sounds like traditional farmers can relearn something from these model urban gardeners too.

So I’m going to make like a Leicester gardener and get my hands on some of that rabbit manure—it’s time to give the Central Valley a run for its money.