Calcareous Soil contain a high amount of lime. This soil sometimes develop calcareous pans in the horizon. pH of the soil ranges between 7.5 and 8.5. Presence of lime in the soil can be easily determined through visible effervescence by treating the soil with 0.1 normal hydrochloric acid.
There are four general soil types of calcareous soils in Bangladesh: (i) Calcareous alluvium occurs extensively in the active Ganges floodplain and Meghna estuarine floodplain. These are raw or stratified alluvium, calcareous throughout or in some layer within 125 cm from the surface. (ii) Calcareous grey floodplain soils occupy parts of the Ganges tidal floodplain, Ganges River floodplain and Lower Meghna river floodplain. These are seasonally flooded grey or have prominent grey coatings on the faces of subsoil cracks and pores, contain lime in some layers within 125 cm from the surface. (iii) Calcareous Dark Grey Floodplain soil occurs extensively in the Ganges Meander Floodplain and locally in the Ganges Tidal Floodplain. These are seasonally flooded soils, contain lime in some layers within 125 cm from the surface and (iv) Calcareous Brown Floodplain Soils are imperfectly drained soils developed in calcareous sediments of the Ganges river system.
These may be moderately well-drained soils with yellowish brown or olive brown subsoil. These are friable loam to silty clay loam occupying the upper part of ridges, calcareous throughout or in some layer within 125 cm from the surface. [Aminul Islam]