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Garden with Insight v1.0 Help: Plant Growth - Heat unit accumulation

Phenological development of the crop is based on daily heat unit accumulation. It is computed by using the equation [Equation 253] where HU, T(mx) and T(mn) are the values of heat units, maximum temperature, and minimum temperature in degrees C on day k, and T(b) is the crop-specific base temperature in degrees C (no growth occurs at or below T(b)) of crop j.

Equation 253

HU = (T(mx) + T(mn)) / 2 - T(b)
HU >= 0
HU = HeatUnitAccumulationForDay
T(mx) = maxTempForDay_degC
T(mn) = minTempForDay_degC
T(b) = baseTempForCrop_degC

Heat unit index

A heat unit index (HUI) ranging from 0 at planting to 1.0 at physiological maturity is computed as follows [Equation 254] where HUI is the heat unit index for day i and PHU is the potential heat units required for the maturation of crop j. The value of PHU may be inputted or calculated by the model from normal planting and harvest dates. Date of harvest, leaf area growth and senescence, optimum plant nutrient concentrations, and partition of dry matter among roots, shoots, and economic yield are affected by HUI.

Equation 254

HUI = HeatUnitIndex
HU = cumHeatUnits
PHU = heatUnitsAtMaturation

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Updated: May 4, 1998. Questions/comments on site to
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.