Sending soybean plants into the future to study their response to climate change. This is the basic idea behind Andrew Leakey’s experiment. “If you look at the literature from the past 30 years, the conclusion is almost always the same: The rise in CO2 will improve soybean yields.” The American researcher wants to determine whether this is true in practice in a so-called FACE facility. “FACE” stands for Free Air CO2 Enrichment. With this method, gas is released from nozzles which react to changes in wind speed and direction. This makes it possible to simulate atmospheric conditions likely in 2050 on test plots.
In the first four rainy years of the experiment, CO2 did actually boost production. In the following dry year, however, the fertilisation effect became a double-edged sword. “More carbon dioxide in early growth stages, when water is available, means more photosynthesis. When it gets drier later, however, more water is needed because of the larger leaf surface.” And this in turn led to a drop in yields. The findings suggest that yield declines in the American Midwest could take place early on.
If you look at the literature from the past 30 years, the conclusion is almost always the same: The rise in CO2 will improve soybean yields.
At the end of 2018, a study summarised the results of the 32 FACE facilities worldwide. While yields drop the closer you are to the equator, in northern latitudes soybeans, maize or wheat could benefit from the rise in CO2. “In some areas of Great Britain, for example, improvements in yields are likely to occur.”
However, in regions badly affected by climate change these negative effects may be mitigated. “On the positive side we now know the reaction mechanisms of soybeans,” says Mr Leakey. The experiment will continue, since more data is urgently needed. Farmers and agronomists need to better understand such mechanisms in order to develop varieties or cultivation practices that counteract the expected decline in yield. There is a lot at stake for American soybean farmers, Mr Leakey recalls: “One third of the world’s supply of soybeans is produced here in the Midwest.”