WATER QUALITY AND SODICITY EFFECTS ON SOIL BULK DENSITY AND CONDUCTIVITY IN INTERRUPTED FLOW 1

Abstract

Interruption of flow during furrow irrigation (e.g., use of surge technique) consolidates soil near the furrow surface, causing reorientation and rearrangement of soil particles, and leads to increased surface bulk density (BD) and reduced hydraulic conductivity (HC) of this surface layer. We hypothesized that soil consolidation could be affected by irrigation water quality and soil sodicity. We studied in the laboratory changes in the BD and HC of an alfisol (Calcic Haploxeralf) and two vertisols (Chromic Haploxerert) having different exchangeable sodium percentage (ESP) levels that were subjected to five cycles of leaching and draining under matric potential of up to -5 J kg -1 . Four different water qualities (electrical conductivity (EC) of 0.01, 0.95, 2.0, and 4.0 dS m -1 ) were tested. Final BD was significantly greater than the initial value when matric potential was applied. Conversely, for continuous leaching (i.e., no application of matric potential), differences between final and initial BD were insignificant. Water quality and sodicity did not affect BD, suggesting that for a given soil exposed to a low level of matric potential, soil consolidation was not affected by water quality or ESP. Final HC values were always lower than initial ones, with the decrease in HC after application of matric potential being by far greater than that observed when continuous leaching was used. The decrease in HC relative to initial HC depended on both water quality, and soil sodicity, was greater with the decrease in water EC and an increase in ESP. Adverse effects of low EC and high ESP on HC were less pronounced in matric potential application than in continuous leaching. Our results suggest that the quality of water available for irrigation and soil sodicity should be taken into account in cases where interrupted flow is considered for improving furrow irrigation efficiency via reducing soil infiltration rate.