Table 20.2 provides an example of how, if suitable measurements of soil properties were made, a soil quality index (SQI) for the plant productivity management goal could be derived using the information in Figures 20.1 and 20.2 and Table 20.1. Four functions of the soil supporting plant productivity are depicted: (1) nutrient cycling, (2) water regulation, (3) physical stability, and (4) resilience and resistance. In calculating the SQI, we will at first assume that each function is given equal weight. For simplicity in this example, only two indicator properties are shown for each function, therefore n=4×2=8. Others, such as those listed in Table 20.1, could have been added. Using interpretive scoring curves such as those in Figure 20.2, the measured values for the indicator properties are standardized on a common scoring scale (S) with a maximum=10. Then the average score is calculated (eq.20.1) by dividing the sum (∑) of all the scores by the number of scores (n). This average is multiplied by 10 to provide a soil quality index that conveniently ranges between 0 and 100