Soil quality under rotational and conventional grazing in Mediterranean areas at desertification risk

Rotational grazing (RG) could be a valid alternative to continuous grazing (CG) in Mediterranean extensive pastures to fight land degradation. This study aimed to compare soil quality under RG and CG management, in paired RG-CG Portuguese pasture areas under strong aridity stress, with RG sites converted from CG management in 2018. Soils were sampled in 2022, at 10 cm depth, over 71 ha of RG and 37 ha of CG pastures, subdivided in 16 and 10 sampling plots, respectively. In each plot, five soil samples were taken to provide one composite sample. Physico-chemical and microbial indicators of soil quality were measured immediately after. Principal Component Analysis (PCA) and Redundancy analysis (RDA) showed a clear separation between RG and CG sites with significantly higher level of soil organic carbon (27%-67%), total nitrogen (67%-77%), cation exchange capacity (9%-36%), and, at a minor extent, water holding capacity (6%-17%), in the RG plots respect to CG plots. No significant difference was found for soil bulk density, microbial and fungal biomass and microbial diversity between sites with different management, although the latter was positively correlated with CG sites in the RDA analysis. Soil organic carbon was significantly correlated to the most relevant physico-chemical parameters for nutrient cycling and water balance and to microbial fungal biomass and N-mineralization, confirming the central role of soil organic carbon for soil health. Results support RG management as an effective choice to improve soil quality in areas under desertification risk.