Heinz Thomet, an organic produce farmer in Newburg, Md., is planting rice on dry land. (Logan Mock-Bunting/For The Washington Post)

The whole point of organic agriculture is soil. Farm in such a way that your soil stays healthy — rich in organic matter, nutrients and microbial activity — and you can grow crops without the synthetic fertilizers and pesticides used in conventional farming.

Organic farmers employ lots of techniques to improve their soil. They use compost and manure, rotate their crops and grow many kinds of plants. They do use pesticides, but only certain ones (mostly non-synthetic, with a few approved synthetics), and often only when other pest-control methods fail.

But plenty of conventional farmers do a lot of those things, too. When you pony up the extra money to buy organic produce, are you supporting environmental benefits? I wanted to know, and it was probably one of the most difficult questions I’ve tried to answer in this column.

We don’t have data about soil health or environmental pollution (in the form of soil erosion, nutrient runoff or greenhouse gases) that allows us to comprehensively assess all organic and conventional acreage and say whether one type or the other is doing better, but scientists all over the country are working on comparisons, so we do have something to go on.

Go on that, and you find that, yes, organic agriculture — which for purposes of this discussion means farming certified as adhering to rigorous standards defined by the U.S. Department of Agriculture — has some important environmental benefits.

One of the scientists working on the comparison is Michel Cavigelli of the USDA. He runs something I’d call an organic-vs.-conventional smackdown if we weren’t talking about the rarefied world of soil science. It’s a long-running smackdown (okay, let’s go with it), having begun in 1993. The USDA’s farm in Beltsville, Md., tests five kinds of agriculture: two conventional and three organic. (The differences involve crop rotations and types of tillage.)

Laborers pick chard at an organic farm in California. Organics are better for farmworkers because they don’t become exposed to the high levels of pesticides often used in conventional farming operations. (Sam Hodgson/Bloomberg)

Which one wins?

Yeah, right. There’s never a clear-cut answer to a question like that when you’re talking about something as complicated as farming. The first thing Cavigelli told me is that “all conventional is not the same, and all organic is not the same,” and then he went on to mention something about devils and details.

Nevertheless, some important differences among those five systems have bubbled to the surface over the past 23 years.

The organic systems in the USDA test:

●Have more-fertile soil.

●Use less fertilizer and much less herbicide.

●Use less energy.

●Lock away more carbon in the soil.

●Are more profitable for farmers.

The conventional systems:

●Have higher yields.

●Are best at reducing erosion (when a no-till system is used).

After speaking with several scientists who study the differences between the two systems, and after reading countless papers on the subject, I think it’s reasonable to conclude that, although results obviously vary, that list is a reasonable representation of the advantages of each system. (If you find other significant, across-the-board claims for organic farming, check the source. Many organic organizations do make such claims. It’s perfectly reasonable for advocacy groups to focus on the research that presents organic in the best light, just as conventional groups focus on the benefits of efficiency and genetic crop modification, but, for this, I’ve tried to focus on sources that don’t have skin in the game.)

I learned a few interesting things along the way. First, although I’ve heard many claims that no-till farming (growing crops without plowing up the soil) can lock carbon in the soil (keeping it out of the environment, where it contributes to climate change), several sources told me that it appears that the sequestered carbon is found in only the top layer of soil. Dig deeper, and you don’t find any. Cavigelli’s organic systems, by contrast, had sequestered carbon at much deeper levels.

But in considering claims about carbon sequestration in organic systems, we need to look at the whole picture. Phil Robertson, a university distinguished professor at Michigan State, points out that a lot of that carbon is added to the soil in the form of manure. Which means that, although there’s more carbon in that particular soil, there’s less wherever you took the manure from. “It’s robbing Peter to pay Paul,” he says.

Robertson also said some tools that mitigate environmental harm aren’t available to organic farmers; one of them is genetically modified crops. Although reasonable people disagree about how the advantages and disadvantages of those crops balance out, Robertson, along with many scientists and farmers, says that both major types of GMOs — the kind that are resistant to the herbicide glyphosate and the kind that have a built-in organic insecticide — can help cut pesticide use.

Also, it’s difficult for organic farmers to implement no-till. Without herbicides, the best weed-killing tool is tilling, and that can lead to erosion, nutrient runoff and the disruption of the microbial community that organic farmers work so hard to foster.

All in all, though, it’s pretty clear that organic systems generally have healthier soil and some environmental advantages over conventional systems.

In 2005, Safeway launched a line of “lifestyle” stores offering more organic and natural foods. In general, food shoppers pay more for organic goods, so organic farmers reap higher profits on what they sell. (Justin Sullivan/Getty Images)

But there’s a problem. The environmental advantages generally are not why consumers are willing to pay extra for organic products. According to the Organic Trade Association (and other groups ), consumers buy organics primarily because they believe the products are better for their health: either more nutritious or safer. So it’s not surprising that organic food purveyors and advocates often promote a product by implying it’s more nutritious or safer, a claim not supported by most of the evidence.

Organic advocacy groups market safety and nutrition, as with the Organic Center’s “Comprehensive guide for identifying safe and nutritious food,” or the Environmental Working Group’s Healthy Child initiative, touting “more scientific evidence that organic food is more nutritious.” Labels for some organic products use the word “toxic” to describe the pesticides they’re not using, despite the fact that some toxic pesticides (pyrethrin, for example) are allowed in organic agriculture. Although organic farming certainly does use fewer pesticides, and that’s an environmental benefit, the preponderance of the evidence indicates that trace amounts of pesticides in food are not dangerous to human health. (Higher levels of exposure, such as those experienced by farmworkers, are a different story.)

Unfortunately, you can’t believe organic food is more nutritious and safe without believing conventional food is less nutritious and safe, and that infuriates advocates of conventional food. Sometimes that fury takes on a distasteful edge — I’ve noticed some schadenfreude at food-borne illness outbreaks pegged to organic foods — but I understand where it’s coming from. Conventional food is as safe and nutritious as its organic counterparts, and if consumers are told otherwise, they’re being deceived, and conventional producers are being harmed.

And misinformation does nothing to improve the quality of the public debate. On farms, in academic institutions and in regulatory agencies, I’ve found that nearly everyone thinks there is value in having farmers employ and improve all kinds of practices. Feeding our growing population is a big job, and there are many constructive ways — organic and conventional, large-scale and small, urban and rural — in which farmers are tackling it. We need all of them.

According to the Organic Trade Association, grocery shoppers don’t buy organic foods because they’re better for the environment; they buy them because they think the products are safer or more nutritious. (Justin Sullivan/Getty Images)

Sometimes it seems as if every column I write has the same conclusion, but it’s an important one. If we’re going to make progress on food, we need a whole lot less of us vs. them. The USDA’s certified-organic program — from its inception a marketing program, not an environmental initiative — has given organic farmers a way to make a living (and farmers do have to make a living) by connecting with like-minded consumers willing to pay a premium for a product that is grown in a way that is often labor-intensive and lower-yielding, and produces some bona fide environmental benefits.

It has also given consumers a choice. For those with concerns about the way most food is grown in this country, organic is a way to vote no. But if organic’s undeniable positives are overshadowed by the negative of organic-vs.-conventional polarization that prevents progress, we all lose.


Haspel writes about food and science and farms oysters on Cape Cod. On Twitter: @TamarHaspel. She will join Wednesday’s Free Range chat at noon: live.washingtonpost.com.