Phosphate sorption product on allophanic Ando soils was revealed by diffuse reflectance infrared(DRIR) spectroscopy. The DRIR spectra of phosphate sorbed on the clay fraction of Kanumatsuchi (weathered pumice) and two allophanic Ando soils in suspension containing sodium phosphate were almost the same as that of noncrystalline aluminum phosphate, but these spectra were different from those of variscite and metavariscite. The DRIR spectra of phosphate contained in the clay fractions of the Ando soils dressed heavily with phosphate fertilizers were also similar to that of noncrystalline aluminum phosphate. From these results, the predominant reaction product of phosphate and allophanic Ando soils was identified as noncrystalline aluminum phosphate.
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