Comparing agricultural religions

by Ari LeVaux

On April 23, the science journal Nature published “Comparing the yields of organic and conventional agriculture.” The mainstream press waded into the paper’s implications but had a hard time packaging them in a headline. CNN announced “Organic yields 25 percent lower than conventional farming,” while the Los Angeles Times proclaimed “Organic Farming, carefully done, can be efficient.”

Pundits have used the paper to support arguments in the debates over organic agriculture. Such cherry-picking isn’t a huge surprise, given the issue’s divisiveness, said co-author Navin Ramankutty of McGill University. “We made everyone equally unhappy,” he told me by phone.

The paper purports to be the second of its kind. The first, in 2007, concluded that organic agriculture could outperform conventional , but parts of that study were criticized. The latest study took those criticisms into account and considered 66 studies that compared the yields of 344 crops. In this sample, conventional techniques outperformed organic in terms of overall yield. In some circumstances, and with some crops, the difference is statistically insignificant. There are counterexamples as well.

Yield alone, the study states, is only “part of a range of economic, social and environmental factors that should be considered.”

This point is often overlooked in discussions of how best to feed the world. Farming methods impact all who share the ecosystem. They can pollute the environment or make use of what would otherwise have become pollutants. They can affect the nutrient levels in food and the health of farm workers. To assume that the best farming practice is the one that produces the highest yield is like observing that a Lamborghini outraces a bicycle, and thus should be the world’s only vehicle.

The paper asserts that the efficacy of farming systems is context-dependent and proposes that the dichotomy between organic and nonorganic is overly simplistic. Hybrid systems, the paper suggests, should be considered in some contexts. Ramankutty used his personal approach to food procurement as an example.

“I may not buy food if somebody was applying pesticides, but I would certainly not mind if a farmer applied a little bit of chemical fertilizer,” he said. “It’s when we use 200 kilograms per hectare compared to maybe 40 or 50 kilograms that the problem arises.”

The paper notes that many organic systems are deficient in nitrogen, and that production on such farms would benefit from more of it. But most conventional systems have more than enough nitrogen.

“The problem is that we use too much of it, in some parts of the planet,” Ramankutty told me. “Then it gets left behind in the soil, it leaches out into groundwater, causing water-quality problems. It runs down rivers and into lakes and causes algal blooms.

Ramankutty said there’s a diminishing return with nitrogen. Applying more casues plants take up less and less of it. However, if there’s no cost to applying nitrogen, then farmers have no incentive to reduce it.

Organic sources of nitrogen include manure, cover crops, fish emulsion, compost and other sources, many labor-intensive. These sources also add organic matter to the soil, which is crucial for microbial activity and moisture retention.  Shoveling shit is a lot more work than applying chemicals. But as long as fuel is cheap, chemical nitrogen will be too.

In developing countries, the farms considered in the study are export-oriented, usually certified organic by international third-party organizations. Ramankutty makes a distinction between subsistence farming (which may be organic by default due to lack of resources), and “intensive organic,” which involve active techniques like composting and mulching. Subsistence farmers might not need to become certified organic, but nonetheless the use of organic methods can build soil, conserve water and grow better crops.

“There is a hypothesis,” Ramankutty said, “that in developing countries, switching from subsistence to intensive organic can be beneficial. We unfortunately couldn’t test that, so all we could say is that there’s no evidence that the hypothesis is true. But that does not mean it’s not true. Absence of evidence is not evidence of absence.”

The next step is “to look at the other side of the equation, the environmental outcomes.” Those results will no doubt further stir the pot over the best way to produce food. Ramankutty expressed regret that the paper has breathed new life into a polarized debate that’s a lot more complicated than a simple dichotomy between organic and conventional.