How many crop heat units (CHU) does corn need to emerge?

That’s a question many growers are asking as their corn seed shivers through the cold spring 2020 growing conditions. On this episode of RealAgriculture’s Corn School, we put that question to Dale Cowan, AGRIS Co-operative agronomist. He says that corn seed typically requires 165 to 175 CHU for emergence, depending on seeding depth.

But cool growing conditions across Ontario have left corn far short of the heat required to break ground. How cold has it been? Cowan notes that as of May 14, London, Ont. has accumulated only 117 CHUs.

“During the last six days we’ve only accumulated 18 CHUs and during three of those days there was zero accumulation,” notes Cowan. Based on his growth model, corn planted on April 24 will not emerge until May 20-22.

That doesn’t mean growers should be discouraged. Cowan says much of the Ontario corn crop was planted into dry, fit ground and “cold and dry is better than cold and wet. As long as soils aren’t saturated, they’re in pretty good shape.”

Cowan recommends growers spend time scouting fields and digging seeds to identify any issues. “You want to see good, firm seeds; nice white mesocotyls, a nice white root system and all the seeds sprouting at the same time.”

And don’t forget to take a measuring tape, says Cowan. Measure out 1/1,000th of an acre (17.5 feet on 30-inch rows) and do seed counts to identify misses and gaps that could produce a poor stand and determine if you have a planter problem or whether the seed is struggling in the cool conditions.

Click here for more Corn School episodes.

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