| Summary: | Sampled soil volume is a main experimental factor which must be properly considered to obtain a reliable estimation of soil physical quality (SPQ) and, thus, to obtain credible evaluation of the impact of a conservative-conventional soil management system on the soil air–water relationship. In this investigation, two ring sizes were used to sample two fine textured soils and soil management for durum wheat cultivation, namely, conventional tillage (CT) and no-tillage (NT). The soil water retention was determined; soil bulk density (BD), macroporosity (MAC<sub>por</sub>), air capacity (AC), and relative field capacity (RFC) were estimated to assess the soil physical quality indicators, in agreement with the guidelines suggested in the literature. The main results showed that the sampling volume for the soil affected the soil water retention estimation (θ) and, consequently, affected the SPQ estimation, given that (i) higher θ values (by a factor 1.11 as mean) were generally obtained with a large diameter than a small one; these differences decreased (by a factor 1.20, 1.10 and 1.03) as the imposed pressure head value decreased (respectively, at <i>h</i> = 0, −10 and −100 cm); (ii) among SPQ indicators considered, soil volume samples seemed to impact the BD–RFC estimation more than AC–MAC<sub>por</sub>, as statistical differences were identified only in the former case; iii) NT soil was significantly more compact, and had lower macroporosity or air capacity, when compared with CT; at the time of sampling, the mean SPQ was always poor for AC–RFC, or optimal for BD, regardless of soil management, and it was intermediate or poor when the MAC<sub>por</sub> was evaluated under CT or NT. This study contributes toward understanding the impact of soil management on soil physical properties in Mediterranean agro-environments.
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