Physicochemical and microbial characterization of Silmandi, Ghatail and Sonatala soil series under Old Brahmaputra Floodplains (AEZ 9) in Bangladesh

Abstract

Understanding the bio-physicochemical characteristics of soil series in the major agroecological zones (AEZs) of Bangladesh is essential for soil health assessment towards supporting sustainable soil management. In this study, the bio-physicochemical characterization of identified genetic horizons from three representative soil series named Silmandi, Ghatail, and Sonatala of AEZ 9 (Old Brahmaputra Floodplain) was performed. Results revealed that irrespective of soil series, the bulk density increased with soil depth ranging from 1.06-1.11 g cm^-3 in surface Ap1 horizons to 1.48-1.56 g cm^-3 in C horizons whereas organic matter declined sharply from 1.81-2.38% in Ap1 to 0.109-0.140% in C horizons. Similarly, bacterial populations decreased from 5.6×10⁷-1.6×10⁸ cfu g^-1 in Ap1 to 5.1×10⁵- 8.3×10⁵ cfu g^-1 in C horizons. Microbial biomass carbon (MBC) declined from 206.83-298.19 mg kg^-1 in Ap1 to 0.18-0.24% mg kg^-1 in C horizons. These findings provide essential baseline information for future soil management practices and crop production in AEZ 9.

J. Bangladesh Acad. Sci. 50(3); 537–552: September 2026