Spatial variation of soil quality index in a semi-arid agricultural land

Soil quality monitoring is vital for agricultural sustainability, soil protection, envirnmental healt, and foot security. This study aimed at analyzing spatial variability of soil quality index (SQI) on a 12-ha semi-arid sloping landscape under rainfed agriculture. One hundred soil samples were taken randomly in the study area located at 20 km southwest of Çankırı city center. The soil samples were transported to a laboratory and analyzed for some soil physical and chemical properties. Soil quality was calculated using pricipal component analysis (PCA) and geometric mean (GM) methods. The SQI-values calculated by PCA (SQIPCA) were generally higher and more variable than SQI-values calculted by GM (SQIGM). Results of geostatistical modeling showed that both of SQIPCA and SQIGM were moderately spatially dependent. A consistent ralationsip was observed between spatial pattern of SQI and slope in the study area. SQI was generally lower on localities with high slope. Spatial pattern of SQI-values were similar to those of CaCO3 content, pH, bulk density of plow pan (Ad horizon), and thickness of plow layer. Surface maps and semivarograms of SQIGM and SQIPCA evidenced presence of a global trend, suggesting that a greater study area is needed in future studies for safely evaluating spatial variation of SQI in study conditions.