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GM Or Non-GM: Which Yields More?

Field studies find lower productivity with genetically modified (GM) seeds.

Genetic modification actually cuts the productivity of crops, an authoritative new study shows, undermining repeated claims that a switch to the controversial technology is needed to solve the growing world food crisis.

The study -- carried out over the past three years at the University of Kansas -- has found that GM soybeans produce about 10 percent less food than its conventional equivalent, contradicting assertions by advocates of the technology that it increases yields.

Barney Gordon, University of Kansas agronomist, says he started the research because many growers who had changed over to the GM crop had "noticed that yields are not as high as expected even under optimal conditions. People were asking the question 'how come I don't get as high a yield as I used to?'"

He grew a Monsanto GM soybean variety and an almost identical conventional variety in the same field. The modified crop produced only 70 bushels of grain per acre, compared with 77 bushels from the non-GM one.

The GM crop -- engineered to resist Monsanto's Roundup herbicide -- recovered only when Gordon added extra manganese, leading to suggestions that the modification hindered the crop's take-up of the essential element from the soil. Even with that addition, the GM soybean variety’s yield was equal to that of the conventional one, rather than surpassing it.

The new study confirms earlier research at the University of Nebraska, which found that another Monsanto GM soybean variety produced 6 percent less than its closest conventional relative, and 11 percent less than the best non-GM soybean available.

The Nebraska study suggested that two factors are at work. First, it takes time to modify a plant and, while this is being done, better conventional ones are being developed. This is acknowledged even by the fervently pro-GM US Department of Agriculture, which has admitted that the time lag could lead to a "decrease" in yields.

But the fact that GM crops did worse than their near-identical non-GM counterparts suggest that a second factor is also at work, and that the very process of modification depresses productivity. The new Kansas study both confirms this and suggests how it is happening.

A similar situation seems to have happened with GM cotton in the U.S., where the total U.S. crop declined even as GM technology took over.

Monsanto says it’s surprised by the extent of the decline found by the Kansas study, but not by the fact that the yields had dropped. The company notes that the soybeans had not been engineered to increase yields, and that a soybean that will is under development. Critics doubt whether the company will achieve this, saying that it requires more complex modification.