Calculating Growing Degree Days

After corn is planted, how many days are required for the crop to emerge and then reach maturity? This is the question on a grower’s mind as we watch snow fall in April.   Corn grows in response to daily heat accumulation or growing degree days (GDD).  Estimating GDD is a practice of collecting the daily high and low temperature, but the maximum high is 86 degrees F and the minimum low is 50 degrees F. Here is an example for three days: 1.    High is 90, low is 65, GDD formula is [(max. temp + min. temp)/2]-50 = GDD accumulated.    [(86+ 65)/2]- 50 = 25.5 GDD 2.    High is 72, low is 46. [(72 + 50)/2] = 11 GDD 3.    High is 63, low 42. [(63 + 50)/2] = 6.5 GDD 4.    The total accumulated GDD for this three day example is 25.5 + 11 + 6.5 = 43 GDD. 5.    Remember, GDD are not negative or reduced, it is a measure of accumulated heat during the growing season.  

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