Methodology to be incorporated into an existing computer model to quantify the effects of fertilizer on growth and yield in Golden Downs Forest in the Nelson region (South Island, New Zealand) was developed and evaluated. Because basal area growth was affected by fertilization, basal area response was modelled using non-linear and linear regression to derive a sigmoid curve which peaks four years after fertilization whose exact shape depends on the rate of, and time elapsed since, fertilization, and the characteristics of the fertilized stand. Volumes of unfertilized and fertilized stands were quantified with equal accuracy and precision using a single-tree taper-based stand volume system derived using sectional measurements of unfertilized and fertilized trees in Golden Downs. This growth and yield methodology was then evaluated on four areas other than Golden Downs in the Nelson region (Pigeon Valley, Motueka, Harakeke, and Rabbit Island) and found to be inapplicable to each. Therefore, adjustments for estimates of stand growth and yield from the model were suggested for each area.