Direct expression of an index for the degree of humification of humic acids using organic carbon concentration

References

• Bravard , S and Righi , D . 1991 . Characterization of fulvic and hurnic acids from an Oxisol-Spodosol toposequence of Amazonia, Brazil . Geoderma , 48 : 151 – 162 .
   Web of Science ®Google Scholar
• Chen , Y , Senesi , N and Schnitzer , M . 1977 . Information provided on humic substances by E 4/E 6 ratios . Soil Sci. Soc. Am. J. , 41 : 352 – 358 .
   Web of Science ®Google Scholar
• Cheshire , MV and McPhail , DB . 1996 . Hyperfine splitting in the electron spin resonance solution spectra of humic substances . Eur. J. Soil Sci. , 47 : 205 – 213 .
   Web of Science ®Google Scholar
• Flaig , W , Beutelspacher , H and Rietz , E . 1975 . “ Chemical composition and physical properties of humic substances ” . In Soil Components, Vol. 1, Organic Components , Edited by: Gieseking , IE . 1 – 211 . New York : Springer-Verlag .
   Google Scholar
• Ghosh , K and Schnitzer , M . 1979 . UV and visible absorption spectroscopic investigations in relation to macromolecular characteristics of humic substances . J. Soil Sci. , 30 : 735 – 745 .
   Web of Science ®Google Scholar
• Kumada , K . 1985 . Elementary composition and absorption spectra of humic and fulvic acids . Soil Sci. Plant Nutr. , 31 : 437 – 448 .
   Web of Science ®Google Scholar
• Kumada , K . 1987 . Chemistry of Soil Organic Matter , 241 – 241 . Amsterdam : Elsevier .
   Google Scholar
• Kumada , K , Sato , O , Ohsurni , Y and Ohta , S . 1967 . Humus composition of mountain soils in central Japan with special reference to the distribution of P type humic acid . Soil Sci. Plant Nutr. , 13 : 151 – 158 .
   Google Scholar
• Kuwatsuka , S , Tsutsuki , K and Kumada , K . 1978 . Chemical studies on soil hurnic acids. I. Elemental composition of humic acids . Soil Sci. Plant Nutr. , 24 : 337 – 347 .
   Web of Science ®Google Scholar
• Kuwatsuka , S , Watanabe , A , Itoh , K and Arai , S . 1992 . Comparison of two methods of preparation of hurnic and fulvic acids, IHSS method and NAGOYA method . Soil Sci. Plant Nutr. , 38 : 23 – 30 .
   Web of Science ®Google Scholar
• Maie , N , Watanabe , A , Hayamizu , K and Kimura , M . 2002 . Comparison of chemical characteristics of Type A humic acids extracted from subsoils of paddy fields and surface ando soils . Geoderma , 106 : 1 – 19 .
   Web of Science ®Google Scholar
• Martin-Neto , L , Rosell , R and Sposito , G . 1998 . Correlation of spectroscopic indicators of humification with mean annual rainfall along a temperate grassland climosequence . Geoderma , 81 : 305 – 311 .
   Web of Science ®Google Scholar
• Matsui , Y , Kumada , K and Shiraishi , M . 1984 . An X-ray diffraction study on humic acids . Soil Sci. Plant Nutr. , 30 : 13 – 24 .
   Web of Science ®Google Scholar
• Oba , Y . 1964 . Methodology for the study of soil humus. II . Pedologist , 8 : 108 – 116 . (in Japanese)
   Google Scholar
• Ohta , S . 1985 . A Climosequence of soils occurred in Kali Gandaki Valley in Central Nepal. II. Soil organic matter accumulation and humus composition . Pedologist , 29 : 18 – 32 . (in Japanese with English summary)
   Google Scholar
• Schnitzer , M and Khan , SU . 1972 . “ Characterization of humic substances by physical methods ” . In Humic Substances in the Environment , Edited by: McLaren , AD . 55 – 64 . New York : Marcel Dekker, Inc. .
   Google Scholar
• Shindo , H and Honma , H . 1998 . Comparison of humus composition of charred susuki (Eulalia, Miscanthus sinensis) plants before and after HNO3 treatment . Soil Sci. Plant Nutr. , 44 : 675 – 678 .
   Web of Science ®Google Scholar
• Tanaka , H , Murata , T , Sakagami , K and Hamada , R . 1995 . Relationship between neutral sugars and the degree of humification in andisols . Soil Sci. Plant Nutr. , 41 : 753 – 761 .
   Web of Science ®Google Scholar
• Tate , KR , Yamamoto , K , Churchman , GJ , Meinhold , R and Newman , RH . 1990 . Relationships between the type and carbon chemistry of humic acids from some New Zealand and Japanese soils . Soil Sci. Plant Nutr. , 36 : 611 – 621 .
   Web of Science ®Google Scholar
• Tatsukawa , R . 1966 . Rapid determination of organic matter with special reference to soil: Determinations for sugars, uronic acids and amino sugars . J. Sci. Soil Manure, Jpn. , 37 : 28 – 33 . (in Japanese)
   Google Scholar
• Tsutsuki , K and Kuwatsuka , S . 1978a . Chemical studies on soil humic acids. II. Composition of oxygen-containing functional groups of humic acids . Soil Sci. Plant Nutr. , 24 : 547 – 560 .
   Web of Science ®Google Scholar
• Tsutsuki , K and Kuwatsuka , S . 1978b . Chemical studies on soil humic acids. III. Nitrogen distribution in humic acids . Soil Sci. Plant Nutr. , 24 : 561 – 570 .
   Web of Science ®Google Scholar
• Tsutsuki , K and Kuwatsuka , S . 1989 . Degradation and stabilization of humus in buried volcanic ash soils. I. Humus composition, molecular size distribution of humic acids, and sugar composition of soils . Soil Sci. Plant Nutr. , 35 : 207 – 216 .
   Web of Science ®Google Scholar
• Watanabe , A , Fujimori , H , Nagai , Y , Miyajima , T and Kuwatsuka , S . 1996 . Analysis of the green fraction of hurnic acids . Eur. J. Soil Sci. , 47 : 197 – 204 .
   Web of Science ®Google Scholar
• Watanabe , A , Itoh , K , Arai , S and Kuwatsuka , S . 1994 . Comparison of composition of humic and fulvic acids prepared by the IHSS method and NAGOYA method . Soil Sci. Plant Nutr. , 40 : 601 – 608 .
   Web of Science ®Google Scholar
• Watanabe , A and Kuwatsuka , S . 1991 . Triangular diagram for humus composition in various types of soils . Soil Sci. Plant Nutr. , 37 : 167 – 170 .
   Web of Science ®Google Scholar
• Watanabe , A , Sarno , Rumbanraja , J , Tsutsuki , K and Kimura , M . 2001 . Humus composition of soils under forest, coffee, and arable cultivation in hilly areas of south Sumatra, Indonesia . Eur. J. Soil Sci. , 52 : 599 – 606 .
   Web of Science ®Google Scholar
• Yamamoto , S , Honna , T , Sanatani , N and Iimura , K . 1995 . Influences of extracting temperature on diluted sodium hydroxide soluble humus properties. 3 . Pedologist , 39 : 27 – 35 . (in Japanese with English summary)
   Google Scholar