Chemical and morphological changes of porous hydrated calcium silicate in paddy soil

Akiko Yamamoto, Masahiko Saigusa, Masami Nanzyo

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The chemical and morphological changes of porous hydrated calcium silicate material (PS) during the dissolution process in paddy soil were investigated by using both a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX) analysis. The results showed that original PS consisted of agglomerate of various sizes with almost the same elemental composition. The SEM images at a high magnification showed that the original PS consisted of agglomerates of small platelike crystals (≦ μm) of tobermorite [Ca5(Si6O18-H2)·4H2O]. On the other hand, elemental composition showed that the PS agglomerates in paddy soil altered to Si- and Ca-rich agglomerates after incubation for 53 d. The morphological differences between the two types of agglomerates were observed by SEM at a high magnification. The Si-rich agglomerates were similar to the original PS in morphology, whereas the Ca-rich agglomerate appeared as a large crystal. The X-ray diffraction patterns obtained in a previous study suggested the presence of quartz and calcite in PS after incubation for 53 d (Saigusa et al. 2000: Soil Sci. Plant Nutr., 46, 89–95). Si- and Ca-rich agglomerates were identified as silica skeletons of PS and calcite, respectively. It was suggested that the silica skeletons of PS remained as a silicon source for rice plants even after the disappearance of tobermorite revealed by the X-ray diffractogram.

Original languageEnglish
Pages (from-to)655-660
Number of pages6
JournalSoil Science and Plant Nutrition
Issue number3
Publication statusPublished - 2000 Jan 1


  • Dissolution process
  • Paddy soil
  • Porous hydrated calcium silicate
  • Rice
  • Silicate fertilizer

ASJC Scopus subject areas

  • Soil Science
  • Plant Science


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