## 2 Materials and Methods
### Methods for Soil Hydraulic Characterisation  
#### 2.2.1 BEST Procedure and Derived Soil Hydraulic and Porosity Parameters  
The hydraulic characterisation of the soil in the plots under consideration was conducted using the BEST method, which allows the parameters of the retention and hydraulic conductivity curves to be estimated based on infiltration tests and data on soil texture, \(\rho_{\text{d}}\) bulk density [ML\({}^{-3}\)] and water content [14]. The BEST method involves performing infiltration tests with a near-zero hydraulic head and can be considered a simplified version of the results obtainable with a tension infiltrometer by imposing zero tension. The basic assumption is that the water retention and hydraulic conductivity functions can be represented using [PERSON]'s [22] model with [PERSON]'s [23] condition and that of [PERSON] and [PERSON] [24], respectively:  
\[\frac{\theta-\theta_{\text{r}}}{\theta_{\text{s}}-\theta_{\text{r}}}=\left[1+ \left(\frac{\text{h}}{\text{h}_{\text{g}}}\right)^{\text{n}}\right]^{-\text{m}} \tag{1}\]  
\[\text{m}=1-\frac{2}{\text{n}} \tag{2}\]  
\[\frac{\text{K}(\theta)}{\text{K}_{\text{s}}}=\left(\frac{\theta-\theta_{\text {r}}}{\theta_{\text{s}}-\theta_{\text{r}}}\right)^{\text{n}} \tag{3}\]  
\[\text{n}=\frac{2}{\text{m}\cdot\text{n}}+2+\text{p} \tag{4}\]  
where \(\theta\) is the volumetric soil water content [L\({}^{3}\)L\({}^{-3}\)], \(\theta_{\text{r}}\) is the residual soil water content (assumed to be zero) [L\({}^{3}\)L\({}^{-3}\)], \(\theta_{\text{s}}\) is the saturated soil volumetric water content [L\({}^{3}\)L\({}^{-3}\)], \(\theta_{\text{s}}\) is the soil water pressure head [L], \(\text{h}_{\text{g}}\) is the van Genuchten scale parameter representing the inflexion point of the water retention curve [L], K is the soil hydraulic conductivity [LT\({}^{-1}\)], \(\text{K}_{\text{s}}\) is the saturated soil hydraulic conductivity [LT\({}^{-1}\)] and m, n (>2) and \(\eta\) are shape parameters. Additionally, p is a tortuosity parameter set equal to 1 following the Burdine relation. Specifically, m, n and \(\eta\) are shape parameters depending on soil texture and are typically estimated from particle size distribution (PSD) with pedotransfer functions. \(\theta_{\text{r}}\), \(\theta_{\text{s}}\), \(\text{h}_{\text{g}}\) and \(\text{K}_{\text{s}}\) are scale parameters that depend on the structure of the porous medium and are estimated by a three-dimensional (3D) field infiltration experiment at zero water pressure head, using the approximations of the quasi-exact implicit infiltration model for transient [Equation (5) and (6)] and steady states [Equation (7) and (8)] proposed by [PERSON] et al. [25]:  
\[\text{I}(\text{t})=\text{S}\sqrt{\text{t}}+\left(\text{AS}^{2}+\text{BK}_{ \text{s}}\right)\text{t} \tag{5}\]  
\[\text{i}(\text{t})=\frac{\text{S}}{2\sqrt{\text{t}}}+\left(\text{AS}^{2}+ \text{BK}_{\text{s}}\right) \tag{6}\]  
\[\text{I}_{\text{s}}(\text{t})=\left(\text{AS}^{2}+\text{K}_{\text{s}}\right) \text{t}+C\frac{\text{S}^{2}}{\text{K}_{\text{s}}} \tag{7}\]  
\[\text{i}_{\text{s}}=\text{AS}^{2}+\text{K}_{\text{s}} \tag{8}\]  
where I is the 3D cumulative infiltration [L], i the infiltration rate [LT\({}^{-1}\)], \(\text{I}_{\text{s}}\) is the asymptotic model for I for large times [L] and \(\text{i}_{\text{s}}\) the steady-state infiltration rate [LT\({}^{-1}\)], S the sortivity [LT\({}^{-0.5}\)], t is the time [T] and A (L\({}^{-1}\)), B and C are constants that can be expressed using the Brooks and Corey relationship. The infiltration tests last until steady-state conditions are reached. Therefore, different algorithms can be used to estimate \(\text{K}_{\text{s}}\) and S. Some of these, such as those known as BEST-slope [14] and BEST-intercept [26], are based on fitting the model to the transient phase of the infiltration process. Others, such as BEST-steady [27], are based solely on experimental data describing cumulative infiltration in steady-state conditions.