## 2 Materials and Methods
### Soil Sampling and Laboratory Measurements  
Undisturbed soil cores were collected at wheat heading (April 2015) within each experimental unit of the RCBD experimental design in 4 sub-replicate locations, for a total of 24 observations. Soil samples were collected at 0-0.20 m depth. The following indicators were quantified on the soil samples:  
(i) chemical indicators: total organic carbon and total nitrogen (TOC and N), alkali-extractable carbon (TEC), humic and fulvic acid carbon (HA_FA), water extractable nitrogen and organic carbon (WEN and WEOC), Olsen available phosphorus (P_Olsen), exchangeable cations (Ca\({}^{2+}\), Mg\({}^{2+}\), Na\({}^{+}\), K\({}^{+}\)), pH and electrical conductivity (EC);  
(ii) physical indicators: texture, dry bulk density (BD), macroporosity (P\({}_{\rm MAC}\)), air capacity (AC) and relative field capacity (RFC);  
(iii) biological indicator: microbial biomass carbon quantified with the fumigation-extraction method [43].  
WEOC and WEN, which are indicators for labile organic C and N pools, were extracted from field-moist soil samples according to the protocol reported in [PERSON] et al. [28]. TOC, TEC, HA_FA and total N were quantified on dried and 2-mm sieved samples, following protocols reported in [PERSON] et al. [17]. In detail, for TOC quantification, soil samples were ground to a fine powder (0.5 mm) using an agate ball mill. TEC was obtained by 0.1 M NaOH + 0.1 M Na\({}_{4}\)P\({}_{2}\)O\({}_{7}\) extraction at 65 \({}^{\circ}\)C for 48 h. humic and fulvic acids were fractionated by acidification to pH = 2.0 with H\({}_{2}\)SO\({}_{4}\). The purification of FA from non-humic substances was carried out by adsorption onto polyvinylpyrrolidone columns. Total organic carbon in soil samples, as well as C fractions in alkali extracts and C and N fractions in water extracts, were quantified through dry combustion using a TOC Vario Select analyzer (Elementar, Lomazzo, Germany), which conducts a catalytic combustion of the sample at high temperatures in air environment. Total N was quantified according to the Kjeldahl procedure.  
Both BD and some points of soil water retention curve, namely the relationship between volumetric soil water content (\(\theta\)) and water pressure head (h), were determined using undisturbed soil cores. Specifically, stainless steel rings with sharp edges (8 cm inner diameter; 5 cm height) were used to determine soil BD and water retention curve at high pressure heads (h \(\geq\) 120 cm). A disturbed soil sample was collected close to the undisturbed sample collection points to determine the water retention curve at low pressure heads (h \(\leq\) 330 cm). The \(\theta\) values were determined on each undisturbed soil core by a hanging water column apparatus [44] for h values ranging from \(-\)5 to \(-\)120 cm, and on repacked soil cores by pressure plate method [45] for h values ranging from \(-\)330 to \(-\)15,300 cm [46]. The soil water retention function was obtained fitting the experimental data with the van Genuchten model [47], and a set of capacitive indicators that give into account of water/air availability were estimated: macroporosity (P\({}_{\rm MAC}=\theta_{\rm s}-\theta_{\rm m}\)) (cm\({}^{3}\) cm\({}^{-3}\)), air capacity (AC = \(\theta_{\rm s}-\theta_{\rm PC}\)) (cm\({}^{3}\) cm\({}^{-3}\)) and relative field capacity (RFC = \(\theta_{\rm PC}/\theta_{\rm s}\)) (dimensionless), where \(\theta_{\rm s}\), \(\theta_{\rm m}\), \(\theta_{\rm PC}\) are the volumetric water contents corresponding to a pressure head of 0, \(-\)10 and \(-\)100 cm, respectively. Evaluation of soil physical quality (SPQ) was carried out according to classifications gathered from literature [14]. In particular, the SPQ was considered optimal when 0.9 \(\leq\) BD \(\leq\)1.2 g cm\({}^{-3}\), P\({}_{\rm MAC}\)\(\geq\) 0.07 cm\({}^{3}\) cm\({}^{-3}\), AC \(\geq\) 0.14 cm\({}^{3}\) cmand \(0.6\leq\text{RFC}\leq 0.7\). Supplementary information on the described indicators can be found in [PERSON] et al. [15].