Application of Soil Quality Index to Assess the Status of Soils Submitted to Intensive Agriculture in the Irrigated Plain of Doukkala, Moroccan Semiarid Region

Abstract

In the irrigated areas, intensive agriculture has led to soil degradation and declining crop yields; therefore, the durability of soil resources is influenced. In order to assess the soil quality changes in the Zemamra area from the highest plain of Doukkala (523 000 ha), in the semi-arid region of Morocco, the soil samples taken from the horizon 0–30 cm were analysed for physical and chemical parameters (Clay, Sand, Silt, SOM, pH, TN, P2O5, K2O, CEC, MgO, CaO, SAR, Na2O, EC, CaCO3, NO3-N, NH4-N, B, Mn, Zn, Fe, and Cu). The data obtained were statistically processed to search for soil quality indices (SQIs). The main findings show that the soil surface has more sand than clay (Sand = 55%, Clay = 31%), an accumulation of phosphorus (P2O5 = 33.34 mg/kg), moderate soil organic matter (1.789%), and carbonate contents of about (2.6%). Soil Structure Stability Index (SSSI<5%) indicated that soil structure is degraded. The selection of the Minimum Data Set by principal component analysis allowed retaining four indicators (cationic exchange capacity, boron, exchangeable potassium, and manganese). After scoring the selected indicators, the soil quality indices thus obtained classified the soils as having low to moderate quality (SQIs<0.55). The indicators: sand, phosphorus, boron, manganese, and zinc are negatively correlated to SQIs, while clay, silt, cationic exchange capacity, pH, soil organic matter, and carbonates are positively correlated. Micronutrients: boron and zinc negatively impact soils at low concentrations.