Soils in pastures vary significantly with depth due to the stronger interaction between soil and plants in the topsoil. However, research on soil resources in pastures has not yet reached a consensus on the appropriate soil depth to consider when evaluating soil quality (SQ). This study aimed to assess how SQ changes with soil depth in two distinct pasture systems.
A semiarid site (Kurşunlu) and a semihumid site (Ilgaz) were selected, and representative sampling areas were designated in each. At both sites, soils at 0-10 and 10-20 cm depths were intensively sampled. The soil quality index (SQI) was calculated for 0-10, 10-20, and 0-20 cm (combining 0-10 and 10-20 cm) soil depths.
The means of SQI related to depth and site were compared using one-way ANOVA. The SQI values ranged from 0.211 (± 0.002, 0-10 cm) to 0.556 (± 0.004, 10-20 cm) at Kurşunlu and from 0.230 (± 0.003, 0-10 cm) to 0.601 (± 0. 003, 10-20 cm) at Ilgaz. On both sites, the depth-related SQI means were significantly different, and in all cases, SQI was significantly higher at Ilgaz.
The 0-10 cm soil depth proved more suitable than 10-20 or 0-20 cm depths for monitoring SQ. Results suggested that soil pH and bulk density were identified as potential early-warning indicators for soil degradation in the study pastures.