Pedogenesis in rice growing hydric soils of Majuli river island, Assam, India

摘要

The elemental composition of four representative rice growing hydric soils in wetlands of Majuli islands were studied in relation to morphology and particle size by developing colour indices and element to clay ratio method. These texturally contrast and neutral to slightly alkaline rice growing soils showed striking difference in distribution of total calcium and low contents with serious loss of total iron and manganese in channel fills and old floodplains due to prolonged saturation. The change of soil moisture regime in alluvial plains, accelerates the leaching and loss of iron and manganese oxides from surface horizons and decrease in clay by lateral movement and fcrrolysis processes that have favoured formation of iron-enriched subsurface horizons in paddy soils. An average linkage method was employed to workout chemical affinity and variability of soil properties among clusters. The cluster data showed that clay and bulk density are least variable whereas K, Ca, Fe and Mn are highly variable among clusters indicating the usefulness in delineating boundaries across landscapes of floodplain wetlands in the river island.