Properties and Utilisation of Andisols in Indonesia

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Soils formed on volcanic ash parent materials and classified as Andisols are widespread in the Indonesian archipelago, covering an area about 3 million hectares. Soils are developed from mostly andesitic to basaltic rocks on Upper Pleistocene to Holocene surfaces. Weathering gradually increases downslope and with the prevailing high precipitation and high temperature produces deep soils. The Indonesian Andisols mostly have dark epipedons with high content of organic carbon and low bulk densities (<0.9 Mg m^<-3>). soil reaction is slightly acid with negative A pH values with CEC ranges from 22 to 30 cmol(+) kg^<-1>. Major minerals in the sand fraction are quartz, plagioclase, hornblende, augite, hypersthene, olivine and volcanic glass. Short-range-order minerals like allophane, imogolite and/or ferrihydrite dominate the clay fraction, whilst halloysite, gibbsite, cristobalite are also detected in lesser amount. The surface charge of Indonesian Andisols containing allophane and imogolite is pH dependent (variable charge) resulting high phosphate fixation. The Langmuir phosphorus sorption maxima ranged from 300 to 2, 500 mg P kg^<-1>. Most of the Indonesian Andisols are among the most productive soils. These soils are intensively cultivated with both annual and perennial of upland crops like tea, coffee, cocoa with quite high productivity. The areas in the vicinity of volcanoes are also well-known as the horticultural centre and support more than 50% of the Indonesian people. The tea and Arabica coffee plantations occupied hundreds hectares of land from lower to medium slopes of volcanoes both in Sutmatra and Java islands while secondary and primary forests formed in the upper slopes of volcano.

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