Vertical distribution of chloroform-extractable green fraction in several Andosol and Cambisol profiles
2006
KOBAYASHI, Takayuki | Watanabe, Makiko | OHTA, Hiroyuki | FUJITAKE, Nobuhide
The vertical distribution of the content of the chloroform-extractable green fraction (CEGF) in the soil profiles of four Japanese Andosols, one Japanese Cambisol and one Nepalese Cambisol was examined using a colorimetric method with an ultraviolet and visible spectrophotometer. In addition, the relationship between the CEGF content and the soil chemical properties was examined by statistical analysis. CEGF was detected in all the soil samples, and the content ranged from 0.02 to 1.16 g kg⁻¹. The CEGF content in the surface A horizon of the Andosol tended to be higher than in the Cambisol. The vertical distribution of the CEGF content in three soil profiles (two Andosol profiles and one Nepalese Cambisol) revealed maximum values in the subsurface horizon. In the Japanese Cambisol, the content of the CEGF was highest in the surface horizon. In the remaining two Andosol profiles containing a buried humus horizon, the content of the CEGF was highest in the buried humus horizon and the distribution was considerably different from that of organic carbon. Statistical analysis showed that the content of the CEGF displayed a significant positive correlation (P < 0.001, n = 36) with the contents of dithionite-citrate-bicarbonate-extractable Al (Ald), and with oxalate-oxalic acid-extractable Fe and Al (Feo and Alo, respectively). Furthermore, the content of the CEGF showed a significant positive correlation with the content of Alo (r = 0.944, P < 0.01, n = 6) in the soil with the highest content of CEGF in the profile. It was, therefore, suggested that CEGF is actively produced in humus-rich soils like Andosols, and that Ald, Feo and, in particular, Alo were associated with the vertical distribution of CEGF in the soil profiles.
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