CONTRIBUTION OF SHALLOW WATER TABLE TO SALINITY / SODICITY DEVELOPMENT UNDER FALLOW AND CROPPED CONDITIONS

摘要

A saline shallow water table can contribute significantly to salinity/sodicity development in the root zone. Field investigation was carried out in saline-sodic soil (EC = 9.7 dS m~(-1), SAR = 32.4 (mmol L~(-1)) and pH = 7.9) to study the effect of fluctuating water table on soil salinization/sodication under fallow and cropped conditions. Wheat and maize were used as cover crops. The water table fluctuation was monitored through piezometer and it ranged from 0.8 to 10 feet during the experimental period. Soil profile salinity /sodicity decreased with lowering of water table and vice versa. Initially at 3.6 feet water-table depth the EC_e of 0-30 cm surface layer was 9.7 dS m~(-1) which decreased to 6.9 & 4.7 dS m~(-1) under fallow and maize crop, respectively when water table lowered to 8 feet. During rabi season further lowering of water table to 10 feet decreased the EC_e to 6.5 & 3.9 dS m~(-1) under fallow and wheat crop. On the other hand EC_e was increased to 11.4 & 10.2 dS m~(-1) during kharif season by rising water water-table to 2.1 feet and to 15 & 11.4 dS m~(-1) during rabi season when water table rose to 0.8 foot. Almost similar trend was found in other soil layers. Likewise SAR was decreased to 25.7 & 21 (mmol L1)1'2 under fallow andcropped conditions, respectively at 0-30 cm soil layer by lowering water table to 10 feet. Whereas it increased to 44 & 36.5 (mmol L~(-1)) when water table rose to 0.8 foot. A small change in SAR of other soil layers was found with water table fluctuation. The soil pH did not change much with changing of water table depth. The comparison of fallow cropped plots indicated that decrease in soil salinity/sodicity with lowering water table was greater under crop cover than fallow conditions.