Soil quality as related to sampling depth on semiarid and semihumid pastures

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.