Relationships among Non-allophanic/Allophanic indicators, Sio, Alp/Alo, and y1, in six Andosol profiles collected under well-preserved forests in Japan

Alam, M. M.*; Yamakita, Eri*; Tamanna, S.*; Thae, E. P.*; Koarashi, Jun   ; Atarashi-Andoh, Mariko  ; Abe, Yukiko; Nakayama, Masataka  ; Mori, Yuki*; Hiradate, Shuntaro*

Andosols with andic properties have been grouped into Allophanic and Non-allophanic, but their formation mechanisms remain unclear. This study aims to clarify the relationships among Non-allophanic indicators, Sio, Alp/Alo, and y1, and understand the pedogenesis of Allophanic and Non-allophanic Andosols in Japan. Soil samples from six Andosol profiles were collected from well-preserved forests in Japan, at 5 cm intervals. For all the soils, Sio values were low in shallower depths. Oppositely, Alp/Alo values were found higher in the upper layers. Although Sio, Alp/Alo, and y1 have been regarded as indicators to be Non-allophanic/Allophanic in Japanese soil classification system, their inconsistent changes were observed. Some horizons had high amounts of Sio and high y1 values simultaneously, which should be termed as strongly acidic and allophane-rich horizons. These horizons would be formed when the allophane-rich horizon receives a large amount of acid, but the allophane still remains in the horizon.