The old market adage that “rain makes grain” refers to how beneficial rainfall can boost crop yields, but not to the deluge that parts of the Eastern Corn Belt saw in August.
The region across the northern half of Illinois and Indiana and parts of eastern Indiana into Ohio experienced its top five wettest start to any August dating back to 1893, says Eric Snodgrass, senior science fellow at Nutrien Ag Solutions, adding that some localized areas in Indiana saw between 15 to 18 inches of rain (see map below).
Crop Tour wades through aftermath
Jim Roemer, meteorologist and president of Weather Wealth newsletter, agreed that this storm system was exceptional. He says 2016 was the last August when the ECB was comparably wet on a broad regional basis; however, that was the end of a strong El Niño event, not the beginning of one as farmers are experiencing now. “So, this is a bit unusual,” Roemer says.
Daniel Quinn, assistant professor and extension corn specialist at Purdue, says corn can experience 10% to 15% yield losses during persistent flooding at the milk and dough stage, but it depends on duration of the flooding and growth stage. A blog post from Ohio State University Extension says that soybeans don’t handle extended flooding well, with the potential for 25% to 85% loss, depending on the varietal, if fields stay submerged for four days or more.
A deluge over the past week hit just ahead of the start of the Pro Farmer Crop Tour. Scouts observed flooding and fields that will likely be fully lost. For parts of the ECB, the wet weather bookends a wet, cool start around a hot, dry stretch that has made for disappointing corn yields and soybean pod counts across Ohio and Indiana, with results from Illinois to be released Wednesday night.
A tricky assessment
What’s tricky about trying to model yields right now is that areas that escaped the worst flooding may outweigh those that were submerged, Snodgrass says. Soils drained in many areas of Illinois and Indiana, but low-lying areas or those near rivers and streams were submerged. The localized flooding may not have as much of an impact on national yield numbers.
“This is a terrifying flood and did a lot of damage, but we had a crop that was actually thirsty for some water in the Midwest, given how hot July was. If you could stay away from the extremities, putting that much rain on a crop in August, a lot of the crop can handle it if it’s well drained,” he says, adding that where Nutrien has programs, its farmers continue to see strong numbers despite the weather.
The heavy rainfall would have been worse had it occurred in June, when crops were smaller, he adds.
Quinn concurs, saying the extreme variability this growing season even within fields will make it hard to gauge crop yield loss. Farmers experienced heavy rainfall in June, heat in July and now rain again.
“I think certainly we’ve lost some in areas, but I don’t think we’ll know the fully realized impacts even over the next couple weeks because we don’t know the level of plant recovery,” he says.
Quinn says he will watch for problems such as stalk rot, ear rot and standability problems because of compromised root systems and a lack of oxygen in the soil, issues that develop later in the growing season and could impact crops closer to harvest.
The highly unusual nature of the August rainfall brings another challenge for agronomists trying to pencil in yield impacts: the lack of research and data available on late-season flooding. “That shows you the rarity of what we’re dealing with,” he says.
Microbial life
Agronomist Missy Bauer of B&M Consulting told the Pro Farmer Crop Tour livestream on Tuesday that it will be difficult for crops in the ECB to escape damage from extremely heavy rains. “We had a lot of concerns in areas that have been getting rains since June,” often five to six inches at a time, she said, noting local extremes.
“I think, for the most part, any time soils are saturated it hurts microbial life,” Bauer said. As a result of this summer’s rains, there will be many fields with several wet spots in them that will be larger than is usually the case. It will show up on combine yield monitors this fall, she said, noting that when a producer hits a spot that’s zero yield it takes a while to get that average back up.
Aside from the rain, corn and soybean farmers’ skies have been often gray because of cloudy or rainy days and smoke from wildfires. That can diminish grain filling since sunlight allows for photosynthesis for the plant to grow and add grain weight, says Mark Licht, associate professor and extension cropping systems specialist in the department of agronomy at Iowa State University.
“How much the rainy weather and/or wildfire smoke affects grain yield is a bit hard to tell because yield loss often is affected by more than one or two or three or more things, i.e. yield loss by a million paper cuts,” he wrote in an email interview. “Overall, I’d say that wet weather has not been exceedingly helpful for grain yield — bu/ac — or production — total bushels.”
Temperature can drive how fast or slow corn reaches maturity, and he says growing degree days accumulation is running a bit higher than normal, with most of that coming in June and early July. Based on this, corn could mature five to 10 days earlier than normal.
Soybeans tend to mature very close to the same time every year unless there are extreme weather situations or farmers significantly change maturity selection.
Mike Tannura, president of T-Storm Weather, says the ECB is heading into a drier, cooler period, which could give a chance for crops to bounce back. “This is an important part of the story. This conversation would be completely different if we were going into another week of rain, but we’re not,” he says.