RETENTION OF POTASSIUM BY VOLCANIC GLASSES OF THE TOPSOILS OF ANDOSOLS IN TOHOKU, JAPAN

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Abstract
Retention of potassium by volcanic glasses in Andosols formed from felsic parent ash was evidenced by electron-probe analysis in this study.Volcanic glass samples were separated from the 20− to 100-micron fraction of the topsoils of selected Andosols, which showed a wide variation in the degree of weathering. The potassium of volcanic glasses analyzed ranged from 1.2 to 6.4 percent as K2O and had close negative correlations with calcium and magnesium in their contents. It was also found that the potassium retention proceeded with the slow desilication of volcanic glasses and that the total amounts of Ca2+, Mg2+, Na+, and K+ of volcanic glasses were maintained at a high level irrespective of the advance of soil weathering. Retention of potassium by volcanic glasses in Andosols formed from felsic parent ash was evidenced by electron-probe analysis in this study. Volcanic glass samples were separated from the 20− to 100-micron fraction of the topsoils of selected Andosols, which showed a wide variation in the degree of weathering. The potassium of volcanic glasses analyzed ranged from 1.2 to 6.4 percent as K2O and had close negative correlations with calcium and magnesium in their contents. It was also found that the potassium retention proceeded with the slow desilication of volcanic glasses and that the total amounts of Ca2+, Mg2+, Na+, and K+ of volcanic glasses were maintained at a high level irrespective of the advance of soil weathering. © Williams & Wilkins 1982. All Rights Reserved.