INFRARED SPECTROSCOPY ANALYSIS AND CHEMICAL PROPERTIES OF INCEPTISOLS FOR AGRICULTURAL LAND DEVELOPMENT

Resumen

The purpose of this study was to explore the properties of Inceptisols (Cambisols) to provide fundamental information for agricultural development. The soil type occupies a significant and vital part of the agricultural land, especially in Kendari City, Indonesia. A total of 30 Inceptisol soil samples on limestone parent material were collected from three locations under tree canopy using vertical profiles to identify the physic and chemical properties. The soil mineral was examined by using X-Ray Diffraction (XRD); clay mineral was determined with Fourier Transform Infrared (FTIR) spectroscopy; chemical elements with X-ray Fluorescence (XRF); total nitrogen content with the Kjeldahl method; and soil magnetic properties with a magnetic susceptibility meter. Total nitrogen in the soil was found to range from 0.106% to 0.597%, soil pH ranged from 5.7 to 6.95, and the sand fraction was determined to be the dominant in all profiles, accounting for 60% to 70%. In contrast, oxides of Si, Al, Fe, Mg, Ti, Ca, S, Na, K, P, Mn, Ni, Co, and Cr were identified in the chemical element content. While the increasing trends of Al, Fe, and Mg with depth were largely attributed to limited leaching and slow rates of weathering, the dominant upward trends of Si across all sites indicated significant soil development in the study area. All sites showed upward trends in magnetic susceptibility, indicating the enrichment of magnetic minerals. Although FTIR spectroscopy successfully identified soil minerals at various depths, the diffraction pattern of the topsoil revealed the silicon oxide quartz (SiO₂) phase.  At 80 to 200 cm, montmorillonite absorption bands were prominent, while at 0 to 40 cm (topsoil), kaolinite absorption bands dominated. The transformation of montmorillonite into kaolinite in Inceptisol, driven by high mineralization during soil development and restricted leaching and weathering, has a substantial impact on agricultural development and long-term productivity.