I was out in the rainy cold field today wondering how much colder than usual it’s been this year. One way of measuring the amount of heat that a plant or insect population has received during a growing season is Growing Degree Days.
Growing Degree Days are calculated by adding the maximum and minimum temperature for each day, dividing that total by two, subtracting a base temperature, then summing up that number for all the days in the growing season so far. For example, four days into a growing season, the daily maximum and minimums might look like this:
- 6,10
- 5,8
- 8,15
- 9,14
If the base temperature is 5, the growing degrees for each day would look like this:
- (6+10)/2 – 5 = 8
- (5+8)/2 – 5 = 12.5
- (8+15)/2 – 5 = 11.5
- (9+14)/2 – 5 = 11.5
giving a total of 43.5 growing degree days.
Different crops and insects have different base temperatures. Calculating the growing degree days can provide valuable information about what stage a crop or insect should be at and thus what conditions to watch for when crop scouting.
Based on Manitoba Ag-Weather’s Seasonal Report, we’re sitting at about 70% of normal for growing degree days, so it is cold this year!
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