Karakteristik Tanah Sawah Dari Endapan Lakustrin Di Sulawesi

Hikmatullah Hikmatullah • Suparto Suparto
Journal article Jurnal Tanah dan Iklim • 2014 Indonesia

Abstrak

. Lacustrine plain in Sulawesi is generally used for paddy fields. However, study on their mineralogical and chemical properties is limited. The aim of the study was to characterize the mineralogical composition and chemical properties of paddy soils derived from lacustrine deposits with different sources of parent materials. Eight paddy soil profiles developed from lacustrine deposits in Tondano, Kotamobagu and Dumoga (North Sulawesi), Limboto and Paguyaman (Gorontalo), Napu and Bariri (Central Sulawesi), and Sengkang (South Sulawesi) have been studied their morphological characteristics in the field and 36 soil samples were collected and analysed for mineralagical composition and physico-chemical properties in the laboratory. Results showed that mineral composition and chemical properties of the paddy soils were varied, depending on the source of parent materials. All layers of paddy soil from Tondano were influenced by intermediary volcanic materials containing high volcanic glass (54-80%), association of plagioclase-pyroxene and hydrated halloysite-allophane. Soil texture was silt loam, high organic C and soil CEC (31-39 cmolc kg-1), and acid reaction (pH 4.5-4.9). Paddy soils from Kotamobagu and Dumoga were also influenced by intermediary volcanic material with little differences in mineralogical compositions, contained few volcanic glass (2-5%), association of plagioclase-amphibole-pyroxene and smectite-kaolinite. Although smectite was present, the soil CEC was low to moderate (11-23 cmolc kg-1). Paddy soils from Limboto, Paguyaman and Sengkang differed from those aforementioned soils. In the former, soils were influenced by weathered acid volcanic materials,sedimentary and metamorphic rocks, where minerlogical compositions were dominated by quartz, association of feldspar-plagioclase, and smectite clay mineral. The dominance of smectite promoted high content of base cations, high soil CEC (25-55 cmolc kg-1) and slightly acid to alkaline reaction (pH 5.7-8.0). Paddy soils from Napu and Bariri weredominated by quartz and feldspar, and association of vermiculite-kaolinite, which probably derived from weathered biotite-granite and sedimentary rocks.. These were indicated by very high K2O (HCl 25% extraction) (187-752 mg 100g-1) deriving from the weathering of biotite and feldspar. Soil texture was sandy loam, low base cations and CEC (2-10 cmolc kg-1), and acid reaction (pH 5.2-5.6). The influence of parent materials, especially volcanic materials have given a positive impact in providing high nutrient reserve for paddy soils to maintain a long term of soil fertility.

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