Shifts in soil structure and soil organic matter in a chronosequence of set-aside fieldsShifts in soil structure and soil organic matter in a chronosequence of set-aside fields Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2018-03-082017enSet-aside is a commonly used practice worldwide to improve soil quality and fertility. However, the benefits of set-aside have not been quantified in a detailed manner and particularly in semi-arid environments where primary production, and hence C inputs to the soil, is constrained by water availability. Using a chronosequence of set-aside fields (0, 6 and 50 years), data were collected regarding the soil structure, addressed with the distribution of aggregate size classes, soil organic carbon (SOC), and total nitrogen content at the surface soil layer (0–15 cm). Soil structure showed a rapid recovery in the 6-years set-aside field and approached the levels of 50-years set-aside field. The recovery of soil structure, however, was not accompanied by a significant increase in bulk soil or in any aggregate size class SOC. In the 50-years set-aside field, the SOC content was 62% higher compared to the 0-years and 6-years set-aside fields. In this field the SOC content reached identical contents in all aggregate size classes except for the silt-clay fraction. In the latter, lower SOC content was assessed which did not differ from the 0-years and 6-years set-aside fields. In a following step, the Carbon, Aggregation, and Structure Turnover (CAST) model was employed to simulate the evolution of soil structure and C sequestration with time. Overall, the CAST model successfully simulated the evolution of soil structure and SOC stocks and provided critical information about the time required to approach the optimum thresholds under the prevailing environmental conditions. The estimated low rates of C sequestration question the effectiveness of the set-aside practice to restore soil fertility in semi-arid environments. These findings outline the need to evaluate additional practices and/or combinations of practices (e.g addition of organic amendments) to improve its effectiveness. Future work should aim to evaluate such practices considering climatic constraints and soil properties.http://creativecommons.org/licenses/by/4.0/Soil and Tillage Research174113-119 Apostolakis Antonios Αποστολακης Αντωνιος Panakoulia Sotiria Πανακουλια Σωτηρια Nikolaidis Nikolaos Νικολαιδης Νικολαος Paranychianakis Nikolaos Παρανυχιανακης Νικολαος Elsevier Aggregates C sequestration CAST model Drylands Fertility restoration