Distribution of Sodium in Relation to Development of Alkalinity in Some Soils of Central Punjab

Abstract

Six alluvial soils developed on floodplains and terraces having different degree of development from semi-arid to sub-humid climate in Punjab were investigated for their physico-chemical properties, soil solution composition, and distribution of sodium. The soils from floodplains have immature profile (A-C), whereas from terraces have weak profile development (A-Bw-C). The soils are moderately to strongly alkaline having pH varying from 8.28 to 10.09. The soils having CaCO3 accumulation had more alkalinity. The soluble sodium and exchangeable sodium had positive and significant correlation with pH, however, influence of former was more in floodplain soils (r = 743*) and that later in terrace soils (r = 866*). The exchangeable sodium dominated more in terrace soils than in floodplain soils. The ionic composition indicated CaHCO3/MgHCO3 and NaHCO3 to be the dominant constituents of the soils. Sodium bicarbonate was mainly factor responsible for development of alkalinity in these soils. Study suggested that the soluble sodium could be responsible for higher pH in floodplain soils, whereas soluble and exchangeable sodium in terrace soils. The total sodium content was found to be associated with primary minerals in sand fraction rather than in clay fraction. A part of sodium seems to be contributed by weathering of Na-minerals in sand and silt fractions of the soils. Key words: Alluvial soils, physico-chemical properties, sodium fractions.