The Classification Problems of the Naiwa Soil Family

Abstract

The purpose of this investigation is to determine the range of characteristics that have been allowed within the Naiwa family. In the Naiwa family are included three series – (1) Naiwa series, (2) Halawa series, (3) Kunuviea series. Of these three series the last stands out distinctly. As such, the present study is concerned with the Naiwa and Halawa series only. Using the existing soil maps and based on the current concepts of these two series, twelve sites were described. Of these, six were from the island of Maui and six were from the island of Molokai. Half the profiles from each island belong to the Naiwa series and the rest to the Halawa series. Judging from morphological characters, six of the twelve profiles were selected for X-ray and D.T.A. analysis. Four of these six were selected for chemical, mineralogical and physical studies. There are distinct morphological differences, as color between the Halawa and Naiwa series. The Naiwa series soils have a Chroma of 10R, while those of the Halawa series tend to be towards 10YR. Associated with the color difference, also, is a difference in Fe203 and Ti02 contents between the two profiles. Both series are characterized by an A horizon of Fe203 and Ti02 accumulation. And this tends to be more pronounced in the Naiwa series. Because this soil has been developed by soil-forming processes, which are quite similar to those associated with the formation of the “laterite crust,” it may be concluded that this is a Chrono-litho sequence and that time and parent material could be the factors that determine the degree of development. It was also noticed that a wide range of characters have been allowed within the Naiwa series and the series could be refined by the introduction of another series which is less developed than the Naiwa series but more developed than the Halawa series. But whether such a separation is necessary and useful in understanding these soils is another question. It was also noticed that a separation based on morphological characters does not agree fully with the chemical analysis. There is a very large overlap in the chemical properties between the two series that is not obvious in the morphological descriptions. These soils could be classified as a complex or the existing method of using morphological characters could be used in separating the Naiwa from the Halawa series until a better understanding of the chemical properties and mineralogy is reached.