## 4 Results
### Macroporosity  
Without amendments, the CAS soil had a higher \(P_{MAC}\) value than the GIN soil (\(P_{MAC}\) = 0.0081 cm\({}^{3}\)/cm\({}^{3}\) in the former case and 0.0063 cm\({}^{3}\)/cm\({}^{3}\) in the latter; \(\Delta\) = +27.1%). In both cases, however, the \(P_{MAC}\) was much lower than the lowest limit of the optimal range of values (\(P_{MAC}\) = 0.07 cm\({}^{3}\)/cm\({}^{3}\)). In particular, the \(P_{MAC}\) values of the two non-amended soils were nearly an order of magnitude lower than the lowest admissible \(P_{MAC}\) value (by 8.6 and 11.1 times for CAS and GIN, respectively). These very low \(P_{MAC}\) values were expected, since the soil samples used in this investigation were repacked and, hence, structureless or with little structure [34]. Consequently, for this SPQ parameter, an effective amendment should induce a substantial increase of the \(P_{MAC}\). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Soil Water** & **Soil** & **Amendment** & **Intercept** & **Slope** & **R\({}^{2}\)** \\ \hline \multirow{6}{*}{(cm\({}^{3}\)/cm\({}^{3}\))} & & COM & 0.465 & 7.53 \(\times\) 10\({}^{-4}\) & 0.8240 s \\ \cline{3-6}  & \multirow{2}{*}{CAS} & VER & 0.492 & 7.81 \(\times\) 10\({}^{-4}\) & 0.6483 s \\ \cline{3-6}  & & BIO & 0.458 & 1.01 \(\times\) 10\({}^{-3}\) & 0.7560 s \\ \cline{3-6}  & & COM & 0.514 & 6.42 \(\times\) 10\({}^{-4}\) & 0.8961 s \\ \cline{3-6}  & \multirow{2}{*}{GIN} & VER & 0.537 & 4.49 \(\times\) 10\({}^{-4}\) & 0.5228 s \\ \cline{3-6}  & & BIO & 0.497 & 9.29 \(\times\) 10\({}^{-4}\) & 0.9639 s \\ \hline \multirow{6}{*}{(cm\({}^{3}\)/cm\({}^{3}\))} & & COM & 0.453 & 6.71 \(\times\) 10\({}^{-4}\) & 0.8261 s \\ \cline{3-6}  & \multirow{2}{*}{CAS} & VER & 0.482 & 5.59 \(\times\) 10\({}^{-4}\) & 0.5960 s \\ \cline{3-6}  & & BIO & 0.453 & 1.00 \(\times\) 10\({}^{-3}\) & 0.7581 s \\ \cline{3-6}  & & COM & 0.504 & 5.57 \(\times\) 10\({}^{-4}\) & 0.8820 s \\ \cline{3-6}  & \multirow{2}{*}{GIN} & VER & 0.530 & 3.00 \(\times\) 10\({}^{-4}\) & 0.3543 s \\ \cline{3-6}  & & BIO & 0.488 & 9.72 \(\times\) 10\({}^{-4}\) & 0.9721 s \\ \hline \multirow{6}{*}{(cm\({}^{3}\)/cm\({}^{3}\))} & & COM & 0.223 & 8.29 \(\times\) 10\({}^{-4}\) & 0.8028 s \\ \cline{3-6}  & \multirow{2}{*}{CAS} & VER & 0.201 & 1.34 \(\times\) 10\({}^{-3}\) & 0.8254 s \\ \cline{3-6}  & & BIO & 0.234 & 1.47 \(\times\) 10\({}^{-3}\) & 0.8807 s \\ \cline{3-6}  & & COM & 0.261 & 9.45 \(\times\) 10\({}^{-4}\) & 0.8304 s \\ \cline{3-6}  & \multirow{2}{*}{GIN} & VER & 0.281 & 5.65 \(\times\) 10\({}^{-4}\) & 0.6338 s \\ \cline{3-6}  & & BIO & 0.250 & 1.55 \(\times\) 10\({}^{-3}\) & 0.9710 s \\ \hline \multirow{6}{*}{(cm\({}^{3}\)/cm\({}^{3}\))} & & COM & 0.086 & 2.86 \(\times\) 10\({}^{-4}\) & 0.4904 s \\ \cline{3-6}  & & VER & 0.110 & 5.43 \(\times\) 10\({}^{-4}\) & 0.9476 s \\ \cline{3-6}  & & BIO & 0.093 & 3.22 \(\times\) 10\({}^{-4}\) & 0.8097 s \\ \cline{1-1} \cline{3-6}  & \multirow{2}{*}{GIN} & COM & 0.105 & 7.07 \(\times\) 10\({}^{-4}\) & 0.9489 s \\ \cline{1-1} \cline{3-6}  & & VER & 0.148 & 5.00 \(\times\) 10\({}^{-4}\) & 0.8444 s \\ \cline{1-1} \cline{3-6}  & & BIO & 0.097 & 3.74 \(\times\) 10\({}^{-4}\) & 0.7800 s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Intercept, slope, and coefficient of determination, \(R^{2}\), of the linear regression line between the volumetric soil water content at fixed pressure head values and the amendment rate, _ar_ (t/ha). The \(P_{MAC}\) vs. _ar_ relationship varied with both the soil and the amendment, since adding the amendment determined an increase of the \(P_{MAC}\) in some cases (COM and VER at CAS and GIN), a decrease in one case (BIO at GIN), or it was ineffective in another case (BIO at CAS) (Figure 3 and Table 1). The statistically significant relationship between the \(P_{MAC}\) and the _ar_ was generally rather weak since, with the only exception of the VER at GIN (\(R^{2}\) = 0.78), the significant values of \(R^{2}\) varied between 0.31 and 0.42 (Table 1).