Soil quality index to assess soil management practices in the semi-arid of Morocco

The indexing methods offer a powerful tool to estimate soil quality and detect the impact of various soil management practices over time. This research was conducted in the semi-arid area of Morocco, to test the impact of two types of tillage (conventional tillage (CT) and no-till), crop residues (vetch and no cover), and three nitrogen fertilization rates (30, 60, and 90 kg/ha) on soil quality index (SQI) and crop yield. To assess SQI, principal component analysis (PCA) was used for selecting the minimum soil data set (MDS). Four indicators were taken as MDS (Soil organic carbon (SOC), Exchangeable Potassium (Kexg), pH, Total Nitrogen (TN) and SOC, Kexg, TN, (Sodium) Na+ for 0–20 and 20–40 cm depth respectively), and scored using linear and nonlinear approaches. SQI produced by the linear method (SQIL) was the most reliable, due to its ability to differentiate soil quality in different layers. SQIL (additive and weighted linear) showed a higher soil quality score (>0.7) at the soil surface (0–20 cm) and medium to low soil quality score (0.46-0.69) at 20–40 cm depths and it reported higher soil quality under CT compared to no-till. Soft wheat under both systems produced an equivalent yield and exhibited no correlation with SQI.