Analysis of the green fraction of humic acids

Summary To understand the effect of land use changes on the composition of humus in tropical soils, samples from land under primary forest, secondary forest, coffee plantation, and arable crops were investigated at three sites in south Sumatra, Indonesia. Total carbon and total nitrogen contents were 1.7 to 4.3 times and 1.1 to 2.8 times greater in the topsoil under primary forest than under the other types of land use. Following change from primary forest to other uses, the proportion of humic acids in the organic matter of the topsoils decreased while that of the fulvic acid fraction increased. Within the range of land uses, differences in the yields of humic acids and fulvic acid fractions were, respectively, larger and smaller than those in total carbon content. The humic acids were classified into the low and middle classes in the degree of humification. Absorption due to the green fraction of humic acids, Pg, was detected in the UV‐visible spectra of almost all the humic acids. No relation was observed between the degree of humification of humic acids or the strength of Pg absorption in their spectra and land use change. The fulvic acid fractions were fractionated on insoluble polyvinylpyrrolidone (PVP) into the adsorbed fractions consisting of humic substances and the non‐adsorbed fractions consisting of non‐humic substances. A positive correlation between the amount of the fulvic acid fraction and the percentage of the PVP‐adsorbed fraction within it indicated that the variation in the amount of the fulvic acid fraction was attributable to acid‐soluble humic substances. The ionization difference spectra of solutions between pH 12 and pH 7 suggested that the chemical structures of the PVP‐adsorbed fulvic acids have been altered by land use change.

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“…The green fraction of humic acids designated ‘Pg’ has absorption maxima at 615, 570, and 450 nm in alkali (Sato, 1974; Watanabe et al . 1996).…”

Section: Methodsmentioning

confidence: 99%

Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia

Watanabe

Sarno

Rumbanraja

et al. 2001

European J Soil Science

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“…2005). The CEGF, which exhibits strong absorption maxima at 454, 440 and 418 nm in chloroform, is considered to be of microbial origin and one of the components of, or a closely related substance to, the green fraction of humic acid (HA) called Pg (Kumada 1987; Watanabe et al. 1996) as previously reported (Kobayashi et al.…”

Section: Introductionmentioning

confidence: 94%

“…2003) and numerical studies on the distribution, origin (Kumada and Hurst 1967; Sato 1976b; Valmaseda et al. 1989) and chemical properties (Kumada and Sato 1980; Watanabe et al. 1996) of Pg have been conducted in view of the importance of Pg, as one of the components of HA (Kumada 1987), and of its role in the mobilization and transport of iron through its chelating ability (Nakabayashi and Wada 1991).…”

Section: Introductionmentioning

confidence: 99%

Vertical distribution of chloroform-extractable green fraction in several Andosol and Cambisol profiles

Kobayashi

Watanabe

Ohta

et al. 2006

Soil Science and Plant Nutrition

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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. 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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“…Sclerotium grains are considered to be one of the precursors of the humic acid 'Pg' fraction (Kumada & Hurst, 1967). The analyses of purified humic acid 'Pg' (Watanabe et al, 1996) extracted from soils in Tsubame, Mt Myoko, Japan, showed similar elemental compositions to the sclerotium grains. As Watanabe et al (1996) reported that their fraction G1 contained larger amounts of alkyl chains while their fraction G2 contained larger amounts of polysaccharides, the chemical features of carbon species in sclerotium grains were more likely to be those of combined G1 and G2 fractions.…”

Section: Ft-ir Spectrummentioning

confidence: 99%

Characterization of major and trace elements in sclerotium grains

Watanabe¹,

Inoue²,

Sakagami³

et al. 2006

European J Soil Science

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Sclerotium grains in soil contain humus-metal complexes that are probably produced from fungal metabolites. The characterization of major elements in sclerotium grains collected from volcanic ash soils in Mt Myoko was examined by X-ray photoelectron spectroscopy, FT-IR spectrometry and CHN analysis, and the concentration of trace elements was determined by PIXE (particle induced X-ray emission spectrometer) analysis. The content of major elements, C, H, N, O and Al, was approximately 47.6, 3.32, 0.78, 30.2 and 1.4% by mass, respectively. Trace elements such as Ti, Cr, Mn, Cu, Zn, Br and Pb were detected in the grains at concentrations between 10 and 100 mg g À1 . Functional carbon groups for the whole grain were characterized by the dominance of O-alkyl C associated with aromatic C. The comparison between the surface and subsurface (matrix) of the grain showed that the concentrations of O, C and N were relatively greater on the surface of sclerotium grains than in the matrix. The proportion of carbon having C-O, C¼O, and O-C¼O bonds, O and N showed a tendency to decrease from the surface towards the matrix. The proportion of C assigned as C-C and/or C-H bonds had a tendency to increase towards the matrix associated with Al.

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Analysis of the green fraction of humic acids

Cited by 15 publications

References 26 publications

Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia

Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia

Vertical distribution of chloroform-extractable green fraction in several Andosol and Cambisol profiles

Characterization of major and trace elements in sclerotium grains

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