Storie Index (STORIE)

The Storie Index is a semi-quantitative method for evaluating potential soil productivity by multiplying ratings for individual soil attributes. The rated attributes are the soil profile, essentially the features of the subsurface layers (factor A), the texture of the surface soil (factor B), the slope (factor C), and conditions of the soil exclusive of A, B, C, such as drainage, alkali content, nutrient level, erosion, and micro-relief (factor X). The most favorable or ideal conditions with respect to each factor are rated at 100 percent. The Storie Index method has been mostly used in California, mainly for irrigated soils. For soil conditions in that state, a classification was established for each factor: for factor A there are nine soil profile type classes with individual ratings depending on soil depth and/or gravel content, for factor B there are five broad topsoil texture classes with individual ratings for texture/stoniness subclasses, for factor C there are seven rating classes.

In order to apply the Storie Index method  correctly on the soils of a region outside California, a new rating table is needed with local calibration for factors A, B, C and X of the soil types in that region, based on crop productivity data for the main soils. Storie Index ratings can be highly subjective depending on the evaluator, and given the multiplicative nature of the system, considerable errors can occur. To reduce the subjectivity inherent to the original Storie Index method, a Revised Storie Index method was developed.