## 2 Materials and Methods
### Methods for Soil Hydraulic Characterisation
#### 2.2.2 Soil Capacity-Based Indicators  
Four capacity-based indicators were selected to obtain a more specific evaluation of the soil's physical quality, which are as follows: macroporosity \(\mathrm{P_{MAC}}\), air capacity \(\mathrm{A_{C}}\), relative field capacity \(\mathrm{R_{FC}}\) and plant available water capacity AWC. The definitions of these four indicators and some generalised ranges and critical limits from the literature [17,31] are given below.  
Macroporosity, \(\mathrm{P_{MAC}}\) (\(\mathrm{L^{3}L^{-3}}\)), is defined as:  
\[\mathrm{P_{MAC}}=\theta_{s}-\theta_{m} \tag{13}\]  
where \(0\leq\mathrm{P_{MAC}}\leq\theta_{s}\) and \(\theta_{m}\) is the saturated volumetric water content of the soil matrix exclusive of macroporces [\(\mathrm{L^{3}L^{-3}}\)] (i.e., for \(h=-0.1\) m).  
The \(\mathrm{P_{MAC}}\) parameter, which defines the volume of soil macroporces, is related to the ability of the soil to drain excess water quickly. Optimal values for \(\mathrm{P_{MAC}}\) are between 0.05 and 0.10, while \(\mathrm{P_{MAC}}\leq 0.04\) is the lower critical limit typical of soils degraded by compaction.  
Air capacity, \(\mathrm{A_{C}}\) (\(\mathrm{L^{3}L^{-3}}\)), of undisturbed field soil is defined by [PERSON] [32] as:  
\[\mathrm{A_{C}}=\theta_{s}-\theta_{FC} \tag{14}\]  
where \(0\leq\mathrm{A_{C}}\leq\theta_{s}\) and \(\theta_{FC}\) is the field capacity soil water content [\(\mathrm{L^{3}L^{-3}}\)] (i.e., for \(h=-1\) m).  
Optimal values of \(\mathrm{A_{C}}\) for reducing aeration deficits in the root zone are between 0.10 and 0.26 (for sandy-loam to clay-loam soils \(\mathrm{A_{C}}\geq 0.14\)), while values lower than 0.10 often decrease plant growth and promote root diseases.  
Plant-available water capacity, AWC (L\({}^{3}\)L\({}^{-3}\)), indicates the water content that can be stored in the soil available to plant roots. AWC is traditionally defined as [32]:  
\[\text{AWC}=\theta_{\text{FC}}-\theta_{\text{WP}} \tag{15}\]  
where \(0\leq\text{AWC}\leq\theta_{\text{FC}}\) and \(\theta_{\text{WP}}\) is the water content at the permanent wilting point [L\({}^{3}\)L\({}^{-3}\)] (i.e., for h = \(-\)153 m).  
AWC values higher than 0.2 are considered optimal, while AWC < 0.10 is considered \"poor\" for root growth and function.  
Relative field capacity, R\({}_{\text{FC}}\) (dimensionless), is defined by:  
\[\text{R}_{\text{FC}}=\frac{\theta_{\text{FC}}}{\theta_{\text{s}}}=1-\frac{ \text{A}_{\text{C}}}{\theta_{\text{s}}} \tag{16}\]  
with \(0\leq\text{R}_{\text{FC}}\leq 1\). R\({}_{\text{FC}}\) indicates the soil's ability to store water and air relative to the soil's total pore volume (as represented by \(\theta_{\text{s}}\)).  
Optimal R\({}_{\text{FC}}\) values, ensuring the ideal balance between root-zone soil water and soil air capacity are between 0.6 and 0.7. Values lower than 0.6 indicate \"water-limited\" soil due to insufficient soil water, while greater R\({}_{\text{FC}}\) values indicate insufficient soil air (\"aeration-limited\" soil).  
The volumetric water contents, \(\theta_{\text{s}}\), \(\theta_{\text{m}}\), \(\theta_{\text{FC}}\) and \(\theta_{\text{WP}}\), required for the estimation of the indicator were obtained from the soil water retention curves derived from the BEST method for the corresponding h values.