Impact of irrigation on soil characteristics in saline Vertisols of Bara tract under Sardar Sarovar Canal Command of Gujarat

Abstract

Detailed characterisation of soil profiles occurring at village Vagra of Bharuch district in Gujarat under pre-and post-canal irrigation situation was carried out to study the effect of irrigation. Salt accumulation was observed in surface layer when saline tube well water was used for irrigation to cotton crop on saline Vertisols. The development of secondary salinisation was observed in the soil profiles irrigated with saline ground water. The same soils when irrigated with fresh canal water for wheat cultivation, showed reduction in soil salinity. The electrical conductivity of saturation extract (ECe) reduced to 0.65 dS m-1 from 9.8 dS m-1 in the surface layer, depicting desalinisation. It was also noticed in canal irrigated soils that exchangeable sodium percentage (ESP) increased to 17.2 from 7.8 in the lower horizon which indicated the initiation of pedogenic process i.e. sodification. Based on the 65 observations, it is noted that changes in the pedogenic processes operate insidiously and the farmers become aware of the problem after considerable damage has been done. It is also observed that bulk density of soils under canal irrigation is higher (1.8 Mg m-3) than those of soils under tube well irrigation/rainfed condition (1.3 Mg m-3) whereas hydraulic conductivity is drastically reduced in soils under canal irrigation. Therefore, a suitable management like conjunctive use of saline water with canal water, cultivation of low water requiring crops, use of pressurised irrigation system are required to be suggested in such a situation to avoid further degradation of soil characteristics