A study into the mobility of iron in podzolized Sarawak upland soils by means of selective iron extractions.

Abstract

The presence of relatively large amounts of crystalline free iron oxides gradually increasing with depth, a virtual absence of new iron accumulations in the amorphous form and a great activity of organic acids in complexing iron in surface horizons were observed. Additional field information provides evidence of large accumulations of iron oxides at great depth in cracks and joints of sedimentary rocks. These characteristics suggest that there has been a relative accumulation of crystalline iron oxides through desilication during an early stage in soil formation. This was followed by a loss of iron in varying degree from the upper horizons, which can most likely be attributed to fossil argilluviation and weathering of iron-rich clay, or possibly to fossil reduction with transport in ferrous form. The latter would presuppose the existence of poorly drained conditions prior to strong dissection resulting in the present landscape. The strong and extensive accumulation of iron oxides at great depth in cracks and joints may be attributed to the oxidation and precipitation of ferrous and ferric iron mobilized upon initial oxidation of pyrites in the weathering front of the sedimentary rocks. Lateral movements of soil water may play a role in this. (Abstract retrieved from CAB Abstracts by CABI’s permission)