Characterization of the volcanic ejecta from Mount Pinatubo [Zambales, Philippines] and its impact on rice production
1991
Reyes, R.Y. | Neue, H.U. (International Rice Research Inst., Los Banos, Laguna (Philippines). Soil and Water Sciences Div.)
The volcanic material is practically devoid of carbon and nitrogen. Although it has an adequate amount of total phosphorus, the availability is low. Soluble cations are moderately high but the capacity to hold and exchange cations is very low. Sulfate-S is within normal range. The pH is near neutral to alkaline, although the more recent volcanic ejecta are acidic lahars and likewise even more acidic. The texture of the ash shows varied contents of sand and silt but the clay content of all samples is less than 5%. Mineralogical analyses indicate a potentially fertile material upon weathering. In its present state, however, the material is low in fertility. Preliminary greenhouse and field experiments on lahar demonstrate that despite the chemical and physical deficiencies of the volcanic material, rice could still grow well. Nitrogen fertilizers, however, have to be applied in higher amounts and in several doses.
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