Relationship of Infiltration with Soil Gypsum Content, Water Salinity, and Water Addition Method

This laboratory experiment was conducted at the College of Agriculture of the University of Anbar to study the effect of soil gypsum content, water salinity level, and application method (continuous and intermittent water addition) on cumulative water infiltration rates in soil. Three soil types containing 90 g kg-1, 197 g kg-1, and 463 g kg-1 gypsum were packed into 40-cm-long transparent columns up to a height of 30 cm in bulk densities approximating field conditions. Saline water was applied at electrical conductivity levels of 2, 4, and 8 dS m⁻¹ using both continuous and intermittent application techniques. Cumulative infiltration was measured over time by tracking the volume of absorbed water. Results indicated that infiltration increased with higher gypsum content, peaking at 14.70 cm after 30 minutes in the soil with 463 g kg-1 gypsum, while the lowest rate of 10.91 cm was observed in the soil with 90 g kg-1 gypsum. Conversely, higher water salinity reduced infiltration, with values decreasing from 10.90 cm at 2 dS m⁻¹ to 6.00 cm at 8 dS m⁻¹. Under continuous irrigation, infiltration reached 13.7, 10.7, and 8.3 cm for increasing salinity levels, whereas intermittent irrigation resulted in 12.09, 9.5, and 7.5 cm, respectively. These findings emphasize the combined effects of gypsum content, salinity, and irrigation technique on soil water dynamics