The model uses a monthly time-step and requires average
daily short-wave incoming radiation, mean vapor pressure
deficit (D), average daily maximum and minimum temperatures,
and total monthly precipitation data. Estimates of soil
water storage capacity (ASW) and soil fertility – specified by a
rating (FR) that takes values between 0 (very poor nutrition)
and 1 (optimum nutrition) – must be provided and updated
annually if these vary, as they do when young trees have not
established full root extension or following application of
commercial fertilizer.