Rising temperatures and sporadic rainfall expected to come with climate change will likely be detrimental to corn yields. But some research indicates that it could be worse than previously thought.
That’s because the changing climate may be a boon for the growth of some of corn’s biggest enemies.
“Most people have been looking at how climate will affect our crops,” said Christopher Landau. “But weeds often benefit more than the crops.”
Landau, a post-doctoral researcher at the University of Illinois, participated in a large research study across the Midwest. He acknowledges that the effect of climate change on weeds is not a new concept. But recent studies have been more extensive and uncovered much more data.
Scientists have long said that the greenhouse gas effect of trapping carbon dioxide inside the Earth’s ozone layer is resulting in rising temperatures and more precipitation.
While most corn producers would welcome extra rainfall and more growing-degree days, the computer models for future climatic patterns indicate that in the Midwest, the extra precipitation is likely to come in the spring and taper off during the summer, when the crops need it most.
Such weather is expected, however, to help troublesome weeds.
“Waterhemp, giant foxtail and some of the other pigweeds were the most damaging weeds in combination with some of the climatic factors we saw,” Landau said. “A lot of people are talking about Palmer amaranth moving farther north. It’s not as common as waterhemp right now, but a lot of research and speculation is showing that it will replace waterhemp as the dominant pigweed in the future.”
The reasons aren’t entirely clear.
“Rising CO2 and warmer temperatures increase the weeds’ competitiveness more than that of corn,” Landau said. “I’m not sure why. They’re better at absorbing resources than a lot of our crops.”
Marty Williams, an ecologist with USDA’s Agricultural Research Service, is co-author of the new study, whose conclusions were published in the scientific journal Global Change Biology. He said in the report that scientists went further in this far-reaching research project than similar ones in the past.
“When ag researchers want to look at weather variation and crop yield in a controlled manner, generally that’s one experiment in two or three environments. If it’s a big study, that might amount to six or eight environments,” he said in the report.
“Our analysis enabled us to look at a historic data set where there were hundreds of environments. That’s the real beauty of it.”
Machine-learning algorithms helped the researchers make sense of the large, complex dataset. They looked at crop management considerations, including planting date, hybrid choice and planting density; percent weed control for multiple weed species; weather data at key growth stages throughout the corn life cycle; and yield.
The analysis showed an average of 50% loss when late-season weeds were minimally controlled. Even with relatively robust late-season weed control (up to 93%), weeds exacerbated crop losses in hot or dry conditions.
Unfortunately, solutions are limited, especially with the increase in herbicide-resistant weeds. Weed scientists have for years sounded the alarm on the problem. They advise farmers to not rely on pesticides alone.
“There are several ways we can use this to adapt our weed-management practices in the future,” Landau said. “We should focus more on later-season tactics. That starts with a (pre-emergence herbicide application), giving you a cleaner field. We’re seeing a lot less efficacy from our herbicides due to resistance. Use remaining efficacy more intelligently.”
He also recommended looking at different mechanical or cultural techniques such as cover crops and some tillage, though those practices come with their own set of challenges.