Agriculture: CO₂ benefits for soybean

Nat. Plants 2, 16132 (2016)

Credit: Andrew Leakey

Crops that utilise the C₃ photosynthetic pathway — including many staple foods such as wheat, soy and rice — are expected to benefit from increasing atmospheric CO₂ concentrations. These benefits could offset the challenges posed by increases in the occurrence and severity of climatic stressors, such as heat and drought. In particular, plants are expected to experience stimulation of photosynthesis that will directly increase yield, and reduced stomatal conductance that will lower water use and thereby ameliorate drought stress. However, tests of these ideas in crop field trials are limited to relatively cool and wet environments.

Sharon Gray from the University of Illinois at Urbana-Champaign, US and co-workers use data from an eight-year open air field experiment where they manipulated precipitation and CO₂ concentrations and utilized year-to-year variations in weather conditions to investigate these interacting effects on soybean crops.

The effect of increased CO₂ treatments on yield was found to diminish to zero as drought intensified. This unexpected result occurred because elevated CO₂ interacted with drought to modify stomatal function, canopy energy balance and nitrogen uptake. The outlook for soy production under these interacting global change factors is concerning.