SIZE FRACTIONATION, DISSOLUTION ANALYSIS, AND INFRA‐RED SPECTROSCOPY OF HUMUS COMPLEXES IN ANDO SOILS

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Abstract
Summary: Eight samples of Ando soil A1 and buried A1 horizons of different ages were fractionated into clay‐, silt‐, and sand‐size separates, and the yields and carbon contents of these separates were determined. The clay‐size separates were subjected to two series of successive extractions, 1) 0.1 M Na4 P2 O7/2% Na2 CO3/0.5 M NaOH and 2) dithionite‐citrate/2% Na2 CO3/0.5 M NaOH; and to difference infra‐red spectroscopy for identification of the extracted constituents.The result indicated that humus evolves from forms with a very low complexing ability for Al and Fe into forms that complex Al and Fe in the A1 horizon, and that humus further interacts with allophane‐like constituents, allophane and imogolite in the buried A1 horizon. These reactions between humus and inorganic constituents result in formation of silt‐ and sand‐size aggregates which are stable to sonic wave treatment, but are broken down into finer particles upon boiling with H2 O2.