Soils of the Laloanea Farm, Northwestern Upolu, Western Samoa

Soils of the Laloanea Farm (40 ha), in the uplands of northwestern Upolu, Western Samoa, were studied by an examination of nine pedons composing two toposequences, one running S-N and the other W-E across extensive portions of the farm. Over short distances considerable variability in the soils has led to their classification into two soil orders of Soil Taxonomy (Entisols and Inceptisols), two suborders, three great groups (Troporthents, Humitropepts, and Dystropepts), four subgroups, and seven families. Major factors contributing to the variability were depth to basaltic boulders or flow rock, presence or absence of a cambic horizon, amount of organic carbon in the profile, particle size distribution in the control section, and occurrence in some pedons of andic properties. Soils all had an oxidic mineralogy class and an isohyperthennic soil temperature regime. Relationship of the factors affecting variability to topographic position is discussed, together with an overview of the physical, chemical, and mineralogical properties of the soils. Similar variability might be expected in other humid tropical situations on young basaltic landscapes with steep, rolling, and benched terrain