Towards defining soil quality of Mediterranean calcareous agricultural soils: Reference values and potential core indicator set

To avoid soil degradation, adapt to climate change and comply with the Sustainable Development goals 2030 (UN General Assembly), establishing the quality/fertility of the agricultural soils of the Mediterranean region and evaluate how these evolve with time is mandatory. This enables adequate management practices to be implemented. The Mediterranean calcareous region has received little attention in this sense, in spite its soil particularities. So, 24 different representative calcareous agricultural soils of the Mediterranean region, including the main management strategies of agricultural soils (rainfed and irrigated), were sampled from the island of Mallorca; and their physical, chemical and biological properties determined. The values obtained for most of the soil characteristics allowed to establish an initial approach to the reference values for the type of calcareous agricultural soils considered, and to clearly distinguish the effect of rainfed or irrigation management practices on soils properties and dynamics. Some enzyme activities were not stimulated by the irrigation conditions assayed or they were only in dry conditions, suggesting optimum enzyme activities could be obtained when alternating dry and humid soil conditions. Soil organic carbon, calcium carbonate and active lime revealed of significant importance in the collection of soils. Finally, the results obtained clearly indicate the heterogeneity of the region and its implications on the different soil characteristics. Therefore, this study could serve as a starting point to adequately establish the quality (fertility) for Mediterranean calcareous agricultural soils and their reference values by conducting further research in this region and including more type of soils.