To judge the quality of a soil for production and environmental goals, the physical, chemical and biological properties of the soil need to be compared against the desirable condition for that land use. Ideally, a response curve is needed that shows the relationship between a quantitative soil characteristic and the quality ranking. Currently, soil quality response curves are poorly defined and there are no internationally agreed standards. This report explains how response curves were obtained for a number of key soil properties used for soil quality assessment in New Zealand, and presents the curves in graphical and numeric form.