Is our growing season changing?
OKOBOJI — Producers are noticing it.
There are more “extreme weather” events, springs are more difficult because of variable weather patterns, the growing season appears to be getting longer, and more large rainfall events have been occurring.
And the new term, “micro-climate,” is beginning to make sense, when consistently, someone half a mile away from a rain event misses out on it.
Dr. Dennis Todey, director of the USDA Midwest Climate Hub in Ames, told producers at the Iowa State University Extension Crop Advantage Series in Okoboji earlier this month that the weather does appear to be changing.
“We’re getting wetter,” he said. “The whole Corn Belt has seen increased precipitation within the last century, and that can be both good and bad. Northwest Iowa has seen more than a 15 percent increase in precipitation within the last 100 years.”
Todey added the Dakotas have experienced large increases in spring and fall precipitation, which he said is sometimes helpful and sometimes not, as dry as it can often be in that part of the U.S.
Extra rainfall can backfire, with no active growth occurring at those times of year because the crop is not yet up in the spring, and is in the process of coming off of the land in the fall — two prime times for soil loss or erosion to occur.
He added wet soil in the fall can create hardships for spring soils in the drying-out process in preparation for planting.
“This is why tile drainage systems becomes such a big deal; because we are putting water on (during the spring and fall) of the year,” he said, adding that heavier rains in the spring and fall have created the need for cover crops and reduced tillage to help save soil profiles.
Todey said soil nutrient loss is a concern with the changing growing season as well, with the increased possibility of runoff carrying nutrients away, and the possibility of saturated soil.
Part of the reason for increased precipitation, he said, could be more moisture coming from the Gulf of Mexico. Europe and Asia are warming as well, but on the flip side, he said South America is becoming more dry due to deforestation happening there.
Contrary to what the overall precipitation pattern has been showing over the last century, Todey said summer precipitation is showing a slight decrease.
He said the state is also experiencing more wind than usual, but the USDA Climate Hub does not have good data gathered yet to back that up.
But he believes it’s true.
Todey went on to say nights are slowly becoming warmer, adding stress to livestock and human existence in the summer and adding additional cooling requirements for livestock and humans. It’s also pushing GDDs (growing degree days) to a “phenological” state (state of phenomenon).
Most of the warming is occurring during the winter months, as the state is experiencing a 1.5-degree higher daily temperature than has been experienced previously.
“Our summertime lows are also getting higher,” said Todey, “and our daytime highs aren’t as high.”
Higher nighttime lows will affect crops over time, pushing them through various stages of growth more rapidly, especially corn, which is driven by growing degree days moreso than soybeans.
Mark Licht, ISU assistant professor and extension cropping systems specialist, said on the far southern edge of the Corn Belt — southern Illinois and southern Missouri — he’s seen the higher night time temperatures cause yield loss issues.
Todey added that with warmer nighttime temperatures, the frost-free season is also longer, possibly by nine days. But he also said a longer growing season can open up opportunities for other areas to grow corn or soybeans. However, expanding corn and soybean crops into other areas not indigenous to them could bring a potential risk of crop failure.
That being said, he also thinks it would be more difficult to experience a widespread crop loss event, with expanded areas producing so much more of the crop that it wouldn’t necessarily affect the market if something like that should happen.
Todey went on to add indications show that the overall warming could be “man made.” He also said they’re seeing an increase in carbon dioxide, which is an environment in which weeds can thrive. That would create weed control issues for both conventional and organic farmers, who would have to deal with them differently from each other.
He sees the Corn Belt experiencing a La Nina throughout the winter, and likely weakening in the spring. Todey believes the changing weather is unlikely to highly impact summer, and that early model indications show a wet, late spring and drier summer.