Influence of Crushed Limestone, Sand Mix, and Bulk Density on Soil Physical Properties Cultivated with Turfgrass in Sulaimani Governorate, Iraq

Abstract

This study examined the impact of crushed limestone and sand mixtures on soil properties affecting turf performance in a football field at the University of Sulaimani. Using a factorial design, three mixtures (Z ₁ , Z ₂ , and Z ₃ ) and three bulk density levels (D ₁ (1.45), D ₂ (1.55), and D ₃ (1.65) Mg m-³) were tested. Key findings revealed a strong inverse relationship between bulk density and infiltration rate, demonstrating that increased compaction decreases soil permeability. The crushed limestone mixtures display superior hydraulic performance and technical strength compared to sand mixtures. The limestone-reinforced Z ₂ layer produced the highest dry matter yield (7.667%) at D ₁ (1.45 Mg m-³), whereas the sand-predominate Z ₁ mixture retained the highest infiltration rates. The dry matter and infiltration reduced significantly at the maximum 1.65 Mg m-³), reaching 2.333% at Z3 × D1. Shear strength increased from 1.9–2.2 kpa to 2.5–3.1 kpa with compression, indicating that soil bulk density possesses higher mechanical strength. Hydraulic conductivity decreased similarly with increasing bulk density (R2 = 0.998). Crushed limestone compositions generally performed better than natural ones.