Impact on corn examined | Hotter temperatures and less rain will increase the need for more drought tolerant crop varieties
Scientists have speculated that rising carbon dioxide, which is associated with climate change, could potentially boost crop yields in the future.
However, U.S. Department of Agriculture researchers in Colorado have determined that the negative effects of rising temperatures outweigh the potential benefits of increased carbon dioxide in the atmosphere.
Laj Ahuja, a research leader with the USDA Agricultural Research Service in Fort Collins, Colorado, concluded that dryland corn yields in the state could decline by 50 percent by 2100 because of rising global temperatures.
Under an average climate change scenario for Colorado, in which summer temperatures rise 4.3 degrees by 2100, Ahuja estimated dryland corn yields would drop from a baseline of 73 bushels per acre to 49 bu. per acre in 2100.
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“We looked at the effect of the precipitation change, the carbon dioxide change, temperature change and then combined all three factors,” Ahuja said.
“For corn, we definitely saw a decrease in yield.”
To estimate the impact of global warming on yield, Ahuja and his fellow scientists used Colorado Water Conservation Board projections on climate change, which represents a synthesis of 16 global climate change models and multiple climate projections for the state.
They then used yield data on three common dryland crop rotations in Colorado: winter wheat-fallow, wheat-corn-fallow and wheat-corn-millet.
Researchers had 15 to 17 years of yield data on the three rotations, which helped them account for weather variability in the future.
“We started out with 17 base years and each year (had) different weather conditions,” Ahuja said. “Then we superimposed the climate change (model) on each of those 17 years. So in the future (the) annual variation was (accounted for).”
The scientists ran the model, generated yield data for 2025, 2050, 2075 and 2100 and found that winter wheat was less susceptible to climate change than millet and corn.
Using precipitation projections for Colorado as a guide, the researchers assumed annual rainfall would remain the same in the future.
However, they estimated that less rain would fall in the spring and summer and more precipitation would occur in the fall and winter.
“Remember it (is) higher temperature and lower precip during the spring and summer. That affects corn more. And (more) carbon dioxide does not benefit corn,” Ahuja said. “For these reasons, the summer crops are more at risk than the winter wheat. That’s what our general finding was.”
It’s not surprising that hot and dry conditions restrict yields, but the study represent a red flag about future growing conditions in North America.
Even though the computer models were based on climate change in Colorado and the resulting decline in yields for dryland crops in the region, the scientists noted the model could be used to assess climate change effects on any cropping system.
“Depending on where people sit politically, on their belief or disbelief of climate change, this type of work is helpful (for) how you deal with extremes,” said Tim Green, an agricultural engineer with the USDA in Fort Collins and one of the study’s authors.
The scientists found that no-tillage offsets some of the impacts of climate change. When they compared a no-till winter wheat-fallow rotation to a conventionally tilled winter wheat-fallow, no-till maintained higher yields as atmospheric temperatures increased.
“Climate change and drought tolerance are essentially the same problem,” Green said. “No-till is obviously one way to help preserve water in the soil.”
Ahuja remains hopeful that plant breeders will develop varieties to counter the detrimental affects of climate change.
“My thinking is that geneticists can come up with varieties that can tolerate a little bit higher temperatures and have higher heat unit requirements.”
As well, he said it’s likely that varieties will shift northward as the planet heats up.
“So you can bring varieties from the south, or from southern Colorado to central and northern Colorado, and they will do better in future years.”
