Late May means two things in Ontario: black flies and hybrid corn heat unit swaps. While the week’s forecast is nothing to write home about, the market wants more corn acres. If you are sticking with corn, and you should, when do you decide to trim back on heat units?
The key in capitalizing on some of the market demand is making sure corn actually finishes — so hybrid selection becomes even more important as the calendar edges towards June.
How many heat units should you trim back by? It depends on where you started, says Peter ‘Wheat Pete’ Johnson.
For those with less than 2800 heat units, your swap-out date was actually last weekend, May 20, and you should already be planting 100 CHU shorter hybrids. For those with 2800 to 3200 range, your trigger date is May 25, where you should be dialling back about 100 heat units for every five to seven days you’re delayed. More than 3200 CHU? Don’t even worry about it until June 1.
And, before you get too bummed out, remember that you’re not necessarily leaving any yield on the table by moving to lower heat units. As Johnson explains in the audio below, planting an appropriate maturity hybrid in fit or mostly fit ground would beat out early planted, long-season lines that went in under terrible soil conditions and cool weather.