Organic farming would struggle to meet global demand

With the world’s human population now more than seven billion – and the prospect of nine billion by 2050 – the focus on agricultural yields is greater than ever. A comprehensive new analysis, published in Nature, is therefore bound to inflame the debate over organic versus chemically enhanced farming methods.

Proponents of organic farming believe it is the best way to feed the world’s population without destroying the environment. In terms of productivity, however, the new paper comes down squarely on the side of conventional farming that uses man-made fertilizer and pesticides but the authors concede organic farming works quite well for some crops.

In their paper the researchers present a meta-analysis of 66 studies comparing the yields of 34 different crop species in organic and conventional farming systems. They included only studies that assessed the total land area used, allowing them to compare crop yields per unit area.

They found crop yields from organic farming are as much as 34 percent lower than those from comparable conventional farming practices. Organic agriculture performs particularly poorly for vegetables and some cereal crops such as wheat, which make up the lion’s share of the food consumed around the world.

Cereals and vegetables need lots of nitrogen to grow, suggesting that the yield differences are in large part attributable to nitrogen deficiencies in organic systems, according Verena Seufert, an Earth system scientist at Canada’s McGill University and the study’s lead author.

“I think organic farming does have a role to play because under some conditions it does perform pretty well … but overall, organic yields are significantly lower than conventional yields,” she said in an interview on the Nature website.

The organic approach appears to work best when producing fruits such as strawberries — which have yields only 3 percent lower than in conventional farming — and oilseed crops such as soybean, which have 11 percent lower yields.

Seufert notes that organic farmers can boost yields of less-productive crops through land-management practices, such as planting them in rotation with leguminous crops that fix nitrogen into the soil.

She is also quick to point out that the present study considered only yield differences; her next project is to analyze existing research on the environmental impacts of organic and conventional agriculture. She is also planning original field research to assess how the two systems compare in developing countries, where reliable data is lacking.

“This is where yield increases are most needed,” said Seufert.

In terms of environmental impact, it is obvious that evidence will come down on the organic farming. Agricultural run-off is a major source of water pollution. China’s first pollution census in 2010 revealed that farm fertilizer was a bigger source of water contamination than factory effluent.

But it is also fairly obvious that agricultural best practice will draw from both schools of farming.

For example, a six-year study completed last year in China found that mixed rice/fish co-culture to be very beneficial in terms of both income and the environment. Farmers can grow the same amount of grain as in conventional rice monocultures – but using at least two-thirds less pesticide and a quarter less fertilizer – and with the income from the fish their net earnings are twice as much.

And, on the less holistic side of the fence, Dutch horticultural engineering firm PlantLab has successfully prototyped a highly-automated vertical farming system that is, in many ways, better than nature. It believes we can grow fruit and vegetables, anywhere in the world and during any season, in half the time it normally takes while using 90 percent less water and no pesticides.