The Titanium Content of Hawaiian Soils and Its Significance

Abstract

AbstractA study has been made to determine the titanium oxide content of typical soils of each great soil group occurring in the Hawaiian Islands. The nature of the occurrence of titanium oxide and its relationship to soil formation was investigated.The titanium oxide content of Hawaiian soils ranged from 2.5 to 25.0%. The titanium oxide content is higher in the surface horizon in the soils which are developed under a climate having an alternating wet and dry season. The greatest accumulation was found in the soils belonging to the Humic Ferruginous Latosols, which occur in areas having an alternating wet and dry season but adjacent to the tropical rain forest. Titanium oxide accumulates in tropical soils under the same conditions that iron oxide accumulates. It is easily dehydrated at or near the surface to form concretions, coatings to surfaces of aggregates or soil particles, or as a massive horizon. Titanium oxide, as anatase, rehydrates slower than iron oxide and is more resistant to reduction when the soil internal drainage becomes poorer. Under extreme reducing conditions titanium oxide will be reduced and will be leached from the soil. Under certain conditions of poor drainage the iron and titanium oxides are reduced and removed by leaching, and the aluminum oxide, gibbsite, is resilicated to kaolinite.