Effects of Tillage and Sheep Stocking Rate on Italian Ryegrass and Soil Properties in a Mediterranean Farming System

A rainfed Italian ryegrass crop (Lolium multiflorum Lam.) was established at the Bonassai experimental farm (NW Sardinia, Italy) to evaluate the effects of different tillage systems and sheep stocking rates on pasture productivity and soil characteristics in an extensive Mediterranean farming system. Three seedbed preparation systems were compared: conventional tillage (CT), minimum tillage (MT), and no-tillage (NT). Each tillage treatment was combined with three grazing management regimes: high stocking rate (HS), low stocking rate (LS), and ungrazed control (UG). During three consecutive growing seasons (2019–2021), pasture herbage mass and botanical composition, together with soil physical, mechanical, chemical, and biological properties, were assessed. Grazing reduced Italian ryegrass herbage dry matter compared with ungrazed plots. In one of the three experimental years, CT produced significantly higher herbage yield than both MT and NT, and also reduced weed abundance in the pasture, particularly Chrysanthemum coronarium. HS two years out of three reduced the abundance of legumes and increased both Asteraceae and bare ground proportion compared with UG. Most soil chemical properties, including macro and micronutrient concentrations, were not significantly affected by either tillage system or stocking rate. However, CT reduced soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) compared with NT in two of the three years. CT also resulted in lower soil compaction, as indicated by reduced bulk density (BD) and penetration resistance (PR), particularly in the upper soil layers, whereas HS increased soil compaction during spring. Finally, NT showed higher values of Biological Quality of Soil (QBS-ar) index in the first year, whereas no clear and persistent pattern emerged during the subsequent years. MT combined with moderate grazing could be considered a balanced approach for Mediterranean extensive systems. Under the environmental conditions examined in this study, these findings highlight the importance of adapting tillage practices and grazing intensity to local soil conditions to balance pasture productivity with soil conservation.