Sampled Soil Volume Effect on Soil Physical Quality Determination: A Case Study on Conventional Tillage and No-Tillage of the Soil under Winter Wheat

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&ndash
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 (MACpor), 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 (&theta
) and, consequently, affected the SPQ estimation, given that (i) higher &theta
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 h = 0, &minus
10 and &minus
100 cm)
(ii) among SPQ indicators considered, soil volume samples seemed to impact the BD&ndash
RFC estimation more than AC&ndash
MACpor, 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&ndash
RFC, or optimal for BD, regardless of soil management, and it was intermediate or poor when the MACpor was evaluated under CT or NT. This study contributes toward understanding the impact of soil management on soil physical properties in Mediterranean agro-environments.