Heat Unit Tips

It is easy to know how many heat units have accumulated if you watch corn emergence closely.
From the day you plant to the day the crop emerges, you automatically know you heave accumulated about 150 heat units.

After that you need a chart like this which gives you an idea of how many heat units accumulate on any given day. All you need to know are the maximum and mimum temperatures received on that day.

For example, on a spring day where the night time low is 5 degrees and the daytime high is 13 we accumulate 5 heat units.

On a summer day where the low is 15 degrees and the high is 30 degrees we accumulate 26 heat units.

Also take note that as daytime highs exceed 30 degrees the accumulated heat units start to decline. This is because the corn plant starts to suffer heat stress, just like we do, and tries to shut down.

I will return to this chart later in the year.