CARMAN, Man. – Andy Nadler found it hard last week to find good news for corn growers worried about the threat of frost this year.
Nadler, who specializes in mapping and analyzing climate trends for Manitoba Agriculture, told growers at a corn field day near Carman that there is good reason to worry, considering the current stage of crops and the probability there could be a severe frost before the end of September.
“I wish I had better news, but seeing what we’ve had, there’s definitely going to be some issues with corn.”
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He said delayed planting this spring combined with a lot of cool, overcast weather during the growing season has put corn crops as much as a month behind in development.
He outlined three things for growers to consider: current growth stage of the crop, how many corn heat units will be available for the remainder of the growing season and when the first severe frost hits.
Taking those things into account can help growers decide whether their grain corn will reach maturity or if they should think about alternative uses for the crop. Weather averages from previous years may help in making that decision.
According to Nadler, almost half the heat units required for a corn crop to reach physiological maturity are needed after it reaches the silking stage.
If, for example, the silking stage of 2300 CHU (corn heat unit) hybrid corn grown near Carman happened around July 25, the crop would still need roughly 1,100 CHU to reach maturity from that date. Based on trends, the accumulation of the needed corn heat units would most likely occur around Sept. 17.
But if the same crop had not reached the silking stage until Aug. 1, it more likely would be Oct. 4 before the 1,100 corn heat units could accumulate.
Nadler reminded growers that those scenarios are not cast in stone because the accumulation of corn heat units this year will not necessarily follow the long-term average.
Based on a 30-year trend mapped by Environment Canada, there is a one in two chance of a fall frost of Ð2 C or colder in either the last two weeks of September or the first week of October in southern Manitoba.
Nadler said there is a one in 10 chance that such a frost could happen on or before Sept. 22.
“Once again, I’d be worried,” he said.
A frost below Ð2 C can stop photosynthesis in corn plants and end further filling of the grain.
In the case of a frost milder than that, grain filling could continue, but to a lesser degree, so yields could still be hampered.
