GREEN COUNTY — “Variable” is a word that one area field agronomist has used to describe his prediction for Southwest Wisconsin’s corn crop yield, and potentially its soybean yield.

On the positive side, “our crops are doing well as far as their maturity and as far as being on-time” compared to last year and to a five-year average, said Josh Kamps, agriculture educator from University of Wisconsin-Madison Division of Extension.

Even so, “our corn crop’s been through a lot since it was planted,” said William Wynn, a field agronomist who works with Green, Grant, Iowa, and Lafayette County areas. 

A May frost nipped the corn, much of which had already grown 6-8 inches tall, and up to 12 for some of the early-planted crop, Wynn said. 

“Maybe the plant never fully recovered from that,” he said, so the ears might be smaller than they otherwise would have been.  

June presented additional challenges, since it brought high temperatures and “was really dry” overall, increasing the stress on the crop, Wynn said. 

“Some of that yield is determined in June,” Wynn explained, so “we don’t want a lot of stress during that time,” since more stress can lead to less yield potential. 

Some farmers may have noticed a visible effect of the June weather in the form of a shorter-than-normal corn silage crop, Kamps said. 

The height “doesn’t make a huge impact on yield on the average year,” Kamps said, since ear development generally determines that. Still, anxiety has been building this summer for those who are not yet sure what their shorter plants will yield. 

Wynn used the word “variable” in his Aug. 27 prediction for overall corn yields, as “the rainfall was so spotty across Southwest Wisconsin.” 

“That’s where it’s really hard to set expectations without knowing their local little microclimate that they’ve had,” Wynn added, since even a half-inch of rain can make “huge difference” on yield, depending on when it falls.

Kamps predicted that it will likely be “an average year” yield-wise, overall, but that “there will be some more sporadic yields,” especially for farmers who plant over large geographical areas, since varied levels of precipitation fell this growing season across different regions of Wisconsin. 

“It’s going to be difficult to estimate” yield totals, since so much depends on how much stress each farmer’s crop went through and when it happened in the growing process, Kamps added. 

Even so, “I think we have reason to be positive with the yields” of corn based on how the crop has progressed and considering that the state has received some timely rains, Kamps said. 

Wynn thinks the Southwest Wisconsin region has a good chance of getting a “pretty decent” soybean crop this year. He had an even more optimistic outlook on it before another hot, dry spell in August, he said.

Earlier this summer he would have predicted the soybean yield to be similar to last year’s or better, when it was “phenomenal.” 

August is a “critical time” for soybeans, said Kamps.  

That is when the plants are trying to fill up the soybean pods and keep those pods attached to the plant, Wynn said. 

Rain is a key ingredient in the process of filling out the plants’ seed pods. Without enough of it, the plant may shrink the size of those seeds or the pods may fall off — decreasing the total yield, Kamps said.

Because of that, inadequate rain in August can decrease potential yield, as “soil moisture is going to drive a lot of that retention of yield,” Wynn said.

For alfalfa, he said at the end of August that he thought the crop had “rebounded nicely from where it was at in June, with the recent rains.”

Making predictions about crop yields is more complex than just looking at weather patterns, though. Disease and the prevalence of pests are also impactful, Kamps said. 

Corn rootworm has been a widespread pest across Southwest Wisconsin this year, Kamps added. 

Since the larvae can chew on the corn roots to the point where they aren’t able to take up nutrients, or even to the stage where they can’t hold up the plant anymore, they can have a negative impact on yield, Kamps said. 

On a positive note, weed control has generally been pretty good this year, he added.

Disease levels in corn were also relatively low, Wynn said. 

There was some tar spot and gray leaf spot visible this growing season, but not to “super concerning” levels, he said. 

In soybeans, he has noticed more white mold, an infection caused by a fungus, this year compared to the last couple of years. 

It causes plants to die prematurely, he said. The impacted plants produce little to no harvestable soybeans, so “that’s a yield drag right there.” 

Overall, Kamps noted that some of the slightly-more-northern counties in the western part of Wisconsin may fare at least equally as well as the generally “big-time yielding counties” — including Green, Rock, Grant and Lafayette — this year. 

That is atypical, he said, since the southwest area generally has a few more days in the growing season compared to the more northern part of Western Wisconsin, and soil in the Southwest may have more yield potential and water-holding capacity to help crops withstand drought.