CLAY MINERALOGY OF SOILS FROM LOWER ATRAI BASIN OF BANGLADESH

Abstract

The lower Atrai basin, the study area, lies in the Agroecological Zone-5
(AEZ-5) of Bangladesh. This study reveals the clay mineral composition of top
soils of seven different soil series viz. Binsara, Taras, Jaonia, Hasnabad, Laskara,
Manda and Mainam developed in the basin. X-ray diffraction (XRD) technique
was employed to identify and quantify the minerals. Results show that mica (41
to 59%) was the most dominant mineral among all soils except Laskara. In
Laskara soils, the interstratified mica-vermiculite-smectite (41%) was the
predominant mineral. Next to mica, kaolinite (10 to 12%) was found to be present
in the Binsara, Taras 1, Jaonia, and Taras 2 soils. Chlorite (7 to 17%) was
identified in all the soils and was found to be the second dominant mineral in the
Manda and Mainam soils. In contrast, the interstratified mica-vermiculitesmectite
(33%) was found to be the second dominant mineral in the Hasnabad
soils. Small amounts of vermiculite mineral (1 to 13%) were identified in almost
all the soils except Binsara. All the soils have interstratified mica-chlorite
minerals (2 to 7%). A tiny amount of smectite (1%) was identified in Taras 1 soil.
As far as the clay mineralogical composition is concerned, most studied soils
were found at the initial stage of weathering, indicating the high potential to
sustain low input subsistence agriculture.