Different soils exist around the world and in Hawaii (Buol et al., 2003). For example, a soil is said to behave like a sponge if it can hold a large amount of water against the force of gravity. Such a soil would not need to be irrigated as frequently as a soil that behaves like a sieve. A wetland taro-farmer wants a soil that can be wetted and made to behave like a viscous liquid. In contrast, an engineer prefers a soil that can be compacted to behave like an elastic solid. Our goal is to predict soil properties and performances. We would like to know if a soil could perform well as a taro patch, vegetable farm, coffee orchard, reservoir, road or foundation for a building.

Soil scientists have devised standard procedures to describe, characterize and name all possible kinds of soil (NRCS, 2005). This classification system is multicategorical or hierarchical, consisting of six categories. Soil order is the highest level, followed by the suborder, great group, subgroup, family and series as indicated by the examples in Table 1 (Uehara et al., 2001). One of the important characteristics of hierarchical classification system is that the information about the object being named increases as one moves down the taxonomic ladder, and the objects become more alike. Thus, soils with identical series names should not only look alike, but behave and perform alike. It is no accident that the Molokai and Lahaina soils on Oahu, Molokai and Maui have been used for nearly identical purposes (Uehara et al., 2001).

There are 190 soil series in Hawaii (Table 2). Some of their chemical and mineralogical properties are listed in a document entitled “Soil survey investigations report No. 29—Soil survey laboratory data and descriptions for some soils of Hawaii” (USDA, 1976).

There are 12 soil orders in the world (Buol, et al., 2003). Given the relatively small land area of Hawaii, it is rather surprising that Hawaii has 9 or perhaps 10 soil orders (Spodosol order has not yet been clearly established). Some orders are more dominant than the others, depending on factors, such as parent material, topography, climate, and the biosphere (Brady and Weil, 2002). The distribution of these soils on the 5 major islands of Hawaii (Kauai, Oahu, Molokai, Maui, and Hawaii) is displayed in Figures 1-5. These maps were constructed from the data shown in Table 2 coupled with a geo-database of Hawaiian mapunits (a mapunit is a soil series with its slope included) provided by the Hawaii NRCS (2006), using the ARCView^® software package (ESRI, 2006). Figure 6 shows some profiles of the soils and their locations.

Table 1. Example of relationships among category subdivisions in soil taxonomy