Micro morphology and mineralogy of the soils of major land resource areas of Kerala

Abstract

An integrated study was conducted on the macromorphology, granulometric composition, primary mineral assemblage, micromorphology and clay mineralogy of the diagnostic horizons from the representative profiles of the major land resource areas of the state for their refined description and classification. The investigated MLRAS of the state are the southern dissected terriplain, southern low land laterites, southern coastal plain, southern dissected midland laterites, southern foot hills, Kuttanad coastal basin, central backwater basin, central dissected midland laterites, Palakkad gap, northern dissected midland laterites and the Wayanad plateau. All the MLRAs are classified within isohyperthermic temperature regime but with aquic, udic and ustic moisture regimes. The universal observation of ochric horizon and its transition to argillic horizon, ill – developed to well developedargillic horizon, presence of sulphuric horizon or sulphidic materials and vertic features could be safely arrived at with the comparative macro and micromorphology of the soils, supported with clay mineralogy. Wide differences in gravel and clay distribution is another unique observation between the MLRAs. Primary mineral assemblage indicate granite, qneiss, quartzite, mica schist and gabbro parentage of the soils of the various major land resource areas. Irrespective of the MLRAS kaolinite is the dominantclay mineral followed by smectite, mica and illite. In the Palakkad gap smectite minerals dominate over kaolinite while in the Kuttanad coastal basin kaolinite and smectite are in almost equal amounts. The non – clay clay minerals mica quartz, feldspars, goethite and gibbsite are also present. Haematite was not seen present in the clay fraction. Smectite and mica are also present even in weathered laterite MLRAs. Diagenesis is observed in the Kuttanad coastal basin and in the Palakkad gap whereas the other MLRAs are with polygenetic or paleoclimatic influenced soils. The study could help in arriving at the safe and refined soil description and classification upto family level on the basis of the results of the investigation. A critical analysis of detailed survey of MLRAs and detailed sampling may be attempted as future line of work with the present investigation as baseline to submit suitable proposals in Soil Taxonomy incorporating detailed soil microfabric criteria as a safe and specific information.