Are crop yields the Achilles heel of organic farming?

Besides occasionally finding a bug in your organic salad mix, what's the difference between conventional and organic farming?

Well, one distinction is that, acre for acre, conventional farming methods are more productive than organic, as recent research shows.

Scientists from McGill University in Montreal, Canada and the University of Minnesota looked at 66 studies that compared yields of 34 crops grown using organic and conventional methods. They found that crop yields produced using organic methods can be up to 34 percent lower  than those produced using conventional techniques.

Organic farming practices appear to be particularly inefficient for grain and vegetable crops. The researchers suggest that lower yields are the result of the types of fertilizers that organic farmers use and how they use them. Farmers using conventional methods apply fertilizer, particularly nitrogen, as crops need it. Organic farmers tend to apply fertilizer only at the beginning of the growing season, and these inputs take longer to be incorporated into the soil and absorbed by plants.

Organic yields were lower than conventional yields across the board, but the scientists found that organic methods could produce yields close to those of certain conventional crops, such as strawberries and soybeans.

“There is still a big yield difference but the study does suggest organic systems have the potential to produce comparable yields, but in a very limited number of crops,” Sonja Vermeulen, of the Copenhagen-based Consultative Group On International Agricultural Research, told Nature.

One important point is that this research analyzed only yields. "Since the world already produces more than enough food to feed everyone well, there are other important considerations," ecologist Catherine Badgley of the University of Michigan told Scientific American. Waste and distribution problems persist, so the world's food future may not just be found by increasing production.

For her next project, Verena Seufert, an Earth system scientist at McGill University, and the study’s lead author, plans to compare environmental impacts of organic and conventional farming practices. She also hopes to look specifically at the two growing methods as they are used in developing countries.

Because as Seufert told Nature, “This is where yield increases are most needed.” 

The meta-analysis was published online today in the journal Nature.