Morphogenesis Of Three Surface-Water Gley Soils From The Meghna Floodplain Of Bangladesh

Abstract

Surface-water gley soils comprise extensive area on the seasonally wet landscape of Meghna floodplain in Bangladesh. Three typical surface-water gley soils from the above floodplain were studied in the field and laboratory for their pedogenesis. Morphological properties indicate that there is formation of gleyed/ pseudogleyed horizons in the soil profiles. Extensive development of mottles, ploughpans and flood coatings or gleyans is the most notable morphogenetic features in these soils. Physically, these soils are medium to fine textured where textural class ranged between silt loam and silty clay. Chemically, the soils are moderately acidic to neutral in reaction with seasonally fluctuating pH in the surface horizon. The ΔpH values are all negative and range from -0.90 to -2.01. The organic matter content in the surface soil is relatively low that decreases steadily with depth. The cation exchange capacity (CEC) of the soils ranged from 3.53 to 14.08 cmol p+/kg with an average of 10.10 cmol p+/kg and base saturation per cent (BSP) varied from 59 to 86. The Ca ++ /Mg ++ ratio is less than unity indicating loss of Ca ++ due to gleization in these soils.

Pedological Characterization of Some Typical Alluvial Soils of Kilombero District, Tanzania

“…The low pH in topsoils may be attributed to low amounts of bases caused by leaching during fluctuations of water table and percolation of water during flooding periods, removal of bases through crop harvests and farming practices. [27] Observed similar trend of pH increasing with depth in annually flooded soils of Bangladesh. Likewise, [34] reported a similar trend of soil pH increasing with depth in paddy soils of Kilombero Valley.…”

“…All the pedons had abundant redoximorphic features in form of strong brown (iron) mottles due to the reducing/waterlogged soil conditions. Researchers [25,26,27] observed similar mottles respectively in subsoils of floodplains in Nigeria and in surface-water grey soils in Bangladesh. Horizon boundary attributes varied among and within pedons, whereby distinctness ranged from abrupt to gradual, but topography was dominantly smooth.…”

“…Clay content increased somewhat with depth in all pedons providing some indication of clay eluviation-illuviation, although there was no clear evidence of clay illuviation features (clay cutans) in the subsoils. Some researchers [27,28] observed consistent clay increase with depth as an indication of clay migration in studies done in Bangladesh and Western-Kenya. nd= not determined BD = bulk density Silt/clay ratio, an indicator of soil susceptibility to detachment and transport, was less than the threshold of 0.4 [30], implying moderate resistance to erosion.…”

Pedogeomorphological Categorization of Selected Soils in Mbogo - Komtonga Irrigation Scheme, Mvomero District, Morogoro Region, Tanzania

“…The strong to medium acid observed in the tops soils of these profiles could be ascribed to low amount of bases by leaching during water table fluctuations and water percolation during flooding periods and soil nutrients mining [36,39,40]. The data also showed that pH increased with depth in the studied profiles as likewise reported in [41,42]. The nature of the observed acidity in the top soils of the representative profiles threatens the availability of mineral elements such as P which is readily available in soils with pH centred at 6.5.…”

Climate and relief influence on particle size distribution and chemical properties of Pseudogley soils in Croatia

“…The fact that in each MAP zone this ratio decreased with soil depth rather steadily and within rather narrow ranges (Fig. 3e) indicates top-down pedogenesis from an initially texturally uniform material (Khan et al, 2012). Therefore, although some Croatian Stagnosols may be polygenetic (Rubinić et al, 2015), most seem to be formed primarily by normal pedogenesis.…”