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Knee-High by the Fourth Applies to This Year’s Corn Crop in Many Areas

In areas like southern Minnesota, that’s often this year’s rule.

In recent years, farmers who have waded into their cornfields on Independence Day have often encountered waist- or shoulder-high corn. This year? Not so much. 

“It’s been a long time since we used the term ‘knee-high by the Fourth of July,’” says Tom Hoverstad, a scientist at the University of Minnesota’s (U of M) Southern Research and Outreach Center near Waseca, Minnesota. “But that might be the case this year.” 

Much corn in the southern Minnesota area surrounding Waseca was struggling when the SROC held its field day on June 18. 

We were fine until the middle of May, but not much fieldwork was done from mid- to late-May,” he says. Some corn wasn’t planted until June 1, and that can make a difference in accumulating growing degree units, he says.

“This year compares with the prevented-plant year of 2013 (in southern Minnesota),” he says. “But that year, we got lots of extra heat that summer.”

One good omen – there has been some heat since that field day a couple weeks ago. Still, the odds are stacked against this year’s corn crop. 

“We can make corn, but it doesn’t look like it will be a bin buster corn this year,” he says. 

Here are some other topics farmers in soggy areas like southern Minnesota are facing. 

Snap your corn dryer into working shape, as this year’s delayed planting may translate into wet corn come fall. September normally has some good drying days, with warm September days typically taking .75% to 1% daily off corn moisture in Minnesota. In early October, though, that drops to .5% to .75% per day. 

“Beyond mid-October, little grain drying occurs,” says Jeff Coulter, a U of M agronomist. “It’s still too early to tell about grain moisture, but we should be prepared for wet corn, particularly if the second part of the growing season is on the cool and cloudy side.”

You know those picket-fence stands you see in the seed corn ads? Well, they haven’t occurred this year in many places. Many farmers were backed into a corner, having to plant into soggy soils or risk not planting at all. This can raise havoc on stands.

Still, these farmers can still get respectable yields, according to U of M trials. For example, farmers who aim for a 34,000-plants-per-acre (ppa) stand and only get 28,000 ppa in a final stand can still get 95% of full yields, says Coulter. Meanwhile, a 24,000-ppa stand can still glean 91% of a full stand. 

“A thin stand can still produce good yields,” says Coulter. 

Not so for height variability with a row, though, says Coulter. “We want all plants at the same height and not competing against each other,” he says. 

A corn plant two leaf stages behind its neighbor will yield just one half of what it would if it were the same height, he says. 

So what’s the hot new weed this year? Waterhemp? Marestail? 
Well, those weeds still infest corn and soybeans. But so far, volunteer corn is the weed of the year in southern Minnesota, says Hoverstad.

“There is so much of it,” he says. “It was a function of what happened last fall. Things were in good shape until early September, and then we hit stormy, windy, and rainy weather. Farmers had trouble getting to some fields, and corn went down in those fields.”

Accordingly, ears that fell off spawned this year’s volunteer corn issue. In next year’s corn and soybeans, it becomes a weed. 

There’s not much that can be done if herbicide-tolerant corn is planted on the same kind of herbicide-tolerant corn. In corn rotated to soybeans, though, there are some good products – such as Select Max – that can control it, says Hoverstad. 

Minnesota’s a stickler when it comes to dicamba applications on dicamba-tolerant soybeans. Like last year, there was a June 20 cutoff for applications in the state in 2019. 

“That is one decision I feel very good about,” says Hoverstad. “When dicamba came out, it seemed like it might be the thing we needed on late-season escaped waterhemp. Glyphosate was not working. But it wasn’t the answer (for late-emerging waterhemp).” 

Applications for this purpose had too much volatility that resulted in off-target movement, although it worked well on early-emerging waterhemp and other weeds, says Hoverstad. 

Thinking about fall nitrogen (N) treatments in advance of corn going on in spring 2020? Well, fall applications can help free up labor and time during a severe spring time crunch. 

Still, bear in mind that the soil is not a good N savings account. There is potential for losses from fall applications compared with spring applications, says Fabian Fernandez, a U of M Extension soil scientist. 

Applying anhydrous ammonia with a nitrification inhibitor like N-Serve is one way to limit N loss in the fall, says Fernandez. There is still potential for losses compared to spring, though, he says. Still, it’s better than applying a form like urea in the fall that readily nitrifies, he says. 

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