Effect of Compost Addition on the Physical and Hydraulic Properties of Gypsiferous Soil under Field Irrigation Conditions

his study aimed to evaluate the effect of compost addition on the hydraulic and physical properties of gypsiferous soils under field irrigation conditions. Two experimental sites were selected within the University of Tikrit area, Iraq, characterized by high gypsum content and similar climatic conditions. Compost (mixture of animal manure and plant residues) was applied at five rates (0, 2.5, 5, 7, and 10 t ha-1) and soil samples were analyzed for bulk density, total porosity, and saturated hydraulic conductivity at a depth of 0-30 cm. Results revealed that compost significantly improved soil physical conditions. Bulk density decreased gradually with increasing compost rate, reaching a reduction of about 11% at 10 t ha-1, while total porosity increased correspondingly by approximately 17%. These improvements were attributed to enhanced soil aggregation and organic matter incorporation that reduced compaction and increased pore continuity. Conversely, saturated hydraulic conductivity showed a gradual decline with increasing compost levels, suggesting partial blockage of macropores and increased water retention capacity. Data were statistically analyzed using analysis of variance (ANOVA), and significant differences among treatments were determined at the 0.05 probability level. Overall, compost application improved soil structure and porosity, while moderating water movement through the soil profile. The findings emphasize that moderate compost additions (5-7 t ha-1) achieve optimal balance between improved soil structure and acceptable water transmission, making compost a sustainable amendment for managing gypsiferous soils under irrigation in arid and semi-arid regions.