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Garden with Insight v1.0 Help: Plant next day functions: calculate general temperature growth constraint

The general temperature growth constraint is used with other growth constraints to calculate the composite growth constraint, which reduces new growth from the optimal. Remember that for each of the growth constraints a value of zero is worst (no growth) and a value of 1.0 is best (optimal growth).

Temperature stress is calculated in a two-stop process. First, if the mean air temperature for the day is below the plant's minimum growth temperature or above the plant's optimal growth temperature times 1.5, the temperature growth constraint is zero, which means no new growth can occur today. Notice that the upper bound for high temperature is arbitrary; this could be improved with a maximum as well as minimum temperature for each plant. Maximum temperatures are not as often collected, though, because they threaten crops less often.

If the mean air temperature falls inside the allowable range for new growth, the temperature growth constraint is calculated using a sine curve symmetrical around the optimal temperature for the plant. The value of the sine curve is 1.0 (best) at the optimal temperature, and declines to zero at the minimum temperature. On the upper side of the optimal temperature the function declines to zero at a value the same distance above the optimal temperature as the minimum temperature is below it. Notice that this creates another arbitrary choice of maximum temperature. Probably the difference between this arbitrary maximum and the real maximum would be small for most plants.

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Updated: March 10, 1999. Questions/comments on site to
Copyright © 1998, 1999 Paul D. Fernhout & Cynthia F. Kurtz.