“Where do organic farmers get their soil from?”
“What’s the best type of soil to use when planting organic food and where do you acquire it?”
Soil is of paramount importance to organic growers, whether they are planting the back 40 or a backyard tomato patch. It really should be on everyone’s radar: According to the Rodale Institute’s long-term Farming Systems Trial, after a transition of about four years, corn and soybean crops grown in organic systems yield as well as, and sometimes better than, those crops grown conventionally. And in times of drought or severe storms, organically farmed soils can actually out-produce conventionally farmed soils because they have a better physical structure.
I realized I didn’t know exactly what that meant, so I reached out to John Reganold, Regents Professor of Soil Science and Agroecology at Washington State University (the first in the U.S. to offer a major in Organic Agriculture Systems). “Organic matter encourages mineral particles (sand, silt, and clay) in the soil to clump together, improving the structure of the soil,” he wrote. “It increases the amount of water and nutrients the soil will hold. All in all, organic matter makes the soil more fertile and productive. The improved structure benefits water infiltrating the soil, so more water gets to plant roots and less runs off the surface.”
I also turned to Keith Stewart, who, 25-plus years ago, ditched a corporate job in Manhattan to become a farmer of organic produce in the Hudson River Valley. A longtime purveyor at the Union Square Greenmarket, Stewart has developed a loyal and ever-growing clientele for his rocambole garlic, potatoes, heirloom tomatoes, summer and winter squashes, herbs, and more. You remember last week, when I mentioned that greens were a cornerstone of my culinary repertoire? I had Stewart’s deeply flavorful kale, collards, and chard in mind.
“Soil is a big subject. Can’t get too deep into it in a quick e-mail, but here’s a few thoughts,” he wrote. “At the level of a commercial farm, no one, as far as I know, buys or imports soil. It would be cost-prohibitive and ecologically disruptive. You use the soil that’s already in place on the land you farm.”
Organic farmers like Stewart must prove to an accredited inspector that no chemical herbicides or pesticides have been applied to the land in the past three years. “Animal manures can be used so long as they are applied 90 days before harvest of an above-ground crop like an eggplant and 120 days before harvest of a crop whose edible portion grows in the ground (like garlic),” Stewart explained.
Then he went on to impart some advice that is worth its weight in gold. “Before buying land, it would be smart to find out what kind of soils are present and what they are good for. You can do this by going to the USDA’s Web Soil Survey and typing in the address of the property you're looking at. It will describe the soils and their capabilities in detail.” Brilliant.
You can also get your soil tested by your County Cooperative Agricultural Extension Service. To find yours, simply type “Cooperative Extension” plus the name of your state into a search engine, and the state website will list the local offices county by county. Depending on the tests you would like done, the cost ranges from free to, well, dirt-cheap. Having your soil tested before piling on the fertilizer (the TV ads are relentless) is one thing that many home gardeners neglect to do, and, in fact, they often use many more pesticides per square foot in their gardens than farmers do in their fields. Presuming that if a little is good, more is better is a common rookie mistake that leads to long-term consequences—the polluting of our soils, rivers, and groundwater.
In terms of what soil is best for organic crops, it’s hard to say. “There are hundreds or perhaps thousands of distinct soils,” Stewart wrote. “Many of them can be used to grow organic crops. Generally speaking, the best soils are loams (with a fairly equal representation of clay, silt, and sand particles). They should drain well, have plenty of organic matter and a healthy population of soil organisms (from bacteria and fungi to nematodes and earthworms). A good soil has plenty of life in it. A handful can have billions of organisms.”
He’s not exaggerating. According to WSU’s Reganold, “Both organically and conventionally farmed soils will likely have millions of microorganisms in a tablespoon of surface soil. However, all conditions being equal (e.g., climate, crop, etc.), the organically farmed soil will have more microorganisms, which can be important for carrying out processes in the soil, and more organic matter.”
If you need organic potting soil to kickstart a smallish garden, one must-read is “How to Make Your Own Potting Soil,” by Barbara Pleasant, published in the December 2008/January 2009 issue of Mother Earth News and available online. She tells you what to look for in a commercial mix (and why you should avoid those with vermiculite, perlite, and peat moss), as well as how to make your own, which is far cheaper and reason alone to compost.
For more information about soils, you may want to pick up a copy of Keith Stewart’s new book, Storey’s Guide to Growing Markets Vegetables & Herbs. It’s written for beginning organic farmers and serious gardeners. You can also read about his insightful journey back to the land in It’s a Long Road to a Tomato.