Chemistry and mineralogy of some soils from Indonesia

Abstract

Samples from profiles of 4 Gramusols (Vertisols) and 2 Mediterranean soils (Alfisols) from East Java and 2 each of Red Podzolic and Yellow Podzolic soils (Ultisols) from East Kalimantan have been investigated for the chemical and mineralogical characteristics. The Grumusols were weakly to moderately acid with a 30–40% base saturation and an amount of Ca plus Mg accounting for 92–97% of the total exchangeable bases. The CEC values were moderately high reflecting the smectitic clay mineralogy, but varied with the samples (23-64 meq/100 g soil) depending on the contents of clay and, possibly, organic matter. The properties of the Mediterranean soils were similar to those of the Grumusols, except that the clays were kaolinitic and the CEC values were correspondingly low (8-10 meq/100 g). The Red and Yellow Podzolic soils were strongly acid with only a small amount of exchangeable bases (<0.5 meq/100 g) but with a considerable amount of KCl-extractable Al (3–5 meq/100 g). The CEC values were low (<8 meq/100 g) due to the low clay content and kaolinitic clay mineralogy. Comparison of two reagents, NH4F-HCl and H2SO4-HCl mixtures as extractants of “plant-available” P, revealed that the latter is more suitable for soils such as Grumusols and Mediterranean soils that are weakly to moderately acid with high quantities of exchangeable (or free) Ca and organic matter. The smectites from the Grumusol samples appeared to carry a small amount of interlayer hydroxy-Al cations. They were “abnormal” in that the basal spacings (001) of the air-dry. Glycerol-solvated samples were larger by a few nanometers than those of normal smectites. The larger values were interpreted in terms of the presence of hydroxy-Al cations in addition to water or organic molecules in the interlayer space. The clays from the Mediterranean soils consisted nearly totally of kaolinite^whereas those from the Red. Yellow Podzolic soils contained an appreciable amount of 2: 1 type minerals in addition to kaolinite. The primary mineral composition of the silts and sands was markedly different between the Grumusols and Mediterranean soils and the Red and Yellow Podzolic soils. The former two contained a large amount of weatherable minerals such as feldspars and amphiboles, in addition to quartz and cristobalite. In contrast, the Red and Yellow Podzolic soils were nearly monomineralic with quartz, indicating severe weathering and scantiness of potential nutrient reserves. © 1992 Taylor & Francis Group, LLC.