Comparison of methods for evaluating soil quality of semiarid ecosystem and evaluation of the effects of physico-chemical properties and factor soil erodibility (Northern Plateau, Spain)

The objective of this study was to compare two different methods for the calculation of the soil quality index for agricultural land in the province of Salamanca in the semiarid ecosystem of the Northern Plateau, Spain. The integrated quality index (IQI) and Nemoro quality index (NQI) were applied using the following indicator selection methods: total data set (TDS) and minimum data set (MDS). A total of 16 soil parameters were used for the TDS method. The evaluation of the soil quality index using only the properties of surface soil provides incomplete information because crop productivity is influenced by both the surface and subsoil properties [e.g. lithic contact, petrocalcic horizon, clayey horizon (Bt)]. The quality indexes were calculated using data from 75 soil profiles considering the soil surface properties (between 0 and 25 cm depth) and control section properties (between 0 and 100 cm). The results show that the consideration of soil properties of both the surface and subsurface horizons is very important to establish a good relationship between soil quality, soil functions, and agricultural management. The results based on the IQI index provide a better estimate of the soil quality compared with the NQI index; higher values were obtained with the TSD than with the MSD. However, the results obtained from the IQIMSD method provide an adequate evaluation of the soil quality. This is relevant because the use of a limited number of indicators reduces the analysis cost and increases the sampling density.