## 4 Conclusions  
The addition of manure or their biochars and hydrochars increased the pH value of the soil with respect to the control soil from a value of 4.7 to values between 6.0 and 6.7. The amendments modified the aluminium chemistry of the soil. In general, products obtained by different thermo-chemical processes (pyrolysis and hydrocarbonization) affected specific fractions of Al in the soil. Biochars and hydrochars formed organo-aluminium complexes of different stability in the soil. Whereas PM and lime transformed exchangeable Al into inorganic non-crystalline Al. The results of the PCA seem to imply that the mechanisms responsible for changes in Al fractionation differ for manure, biochar and hydrochar. Further studies would be required to elucidate the exact mechanisms underpinning the observed transformations. All thermal amendments were capable of replacing slaked lime to reduce the soil exchangeable Al extracted by NH\({}_{4}\)Cl to a value of less than one fourth of that in the control soil.  
Figure 3: Principal component analysis for soil aluminium fractions and chemical properties of manure (PM) and its biochars (BPC450 and BPC600) and hydrochars (HPC200 and HPC240).  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Variable**} & \multicolumn{2}{c}{**Eigenvectors**} & \multicolumn{2}{c}{**Correlation Coefficient**} \\ \cline{2-5}  & **PC1** & **PC2** & **PC1** & **PC2** \\ \hline Al-CaCl\({}_{2}\) & \(-0.277\) & \(0.131\) & \(-0.658\) & \(0.264\) \\ Al-NH\({}_{4}\)Cl & \(-0.363\) & \(0.191\) & \(-0.864\) & \(0.386\) \\ Al\({}_{0}\) & \(0.374\) & \(0.079\) & \(0.891\) & \(0.159\) \\ Al\({}_{\rm P}\) & \(-0.298\) & \(0.306\) & \(-0.708\) & \(0.618\) \\ Al\({}_{\rm Cu}\) & \(-0.233\) & \(-0.385\) & \(-0.554\) & \(-0.777\) \\ Al\({}_{\rm p}\)-Al\({}_{\rm Cu}\) & \(-0.064\) & \(0.488\) & \(-0.151\) & \(0.985\) \\ Al\({}_{0}\)-Al\({}_{\rm P}\) & \(0.357\) & \(-0.193\) & \(0.849\) & \(-0.390\) \\ pH & \(-0.317\) & \(-0.131\) & \(-0.754\) & \(-0.265\) \\ EC & \(0.394\) & \(0.048\) & \(0.938\) & \(0.096\) \\ CEC & \(-0.010\) & \(0.399\) & \(-0.024\) & \(0.805\) \\ OC & \(0.058\) & \(0.405\) & \(0.138\) & \(0.817\) \\ Carbonates & \(-0.343\) & \(-0.285\) & \(-0.816\) & \(-0.576\) \\ \hline \end{tabular}
\end{table}
Table 3: Eigenvectors and correlation coefficients between principal components (PC1 and PC2) and variables (soil Al fractions and chemical properties of the amendments).  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/10/21/7843/s1](http://www.mdpi.com/2076-3417/10/21/7843/s1)]([http://www.mdpi.com/2076-3417/10/21/7843/s1](http://www.mdpi.com/2076-3417/10/21/7843/s1)), Table S1: Main properties of pig manure, biochars and hydrocarbons.  
**Author Contributions:** Conceptualization, all authors; methodology, all authors; validation, all authors; formal analysis, all authors; investigation, all authors; resources, all authors; data curation, all authors; writing--original draft preparation, all authors; writing--review and editing, all authors; project administration, G.G. and A.-M.M.; funding acquisition, G.G. and A.-M.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded byMinisterio de Economia y Competitividad (Spain)=, grant number CGL2014-58322-R.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.