## 3 Results and Discussion
### Physicochemical Characterization of Compost and Vermicompost  
Table 1 shows the physicochemical properties of the organic amendments applied to the experimental plots. The increase in pH and the decrease in the C/N ratio during the treatment of the waste can be used as indicators of the evolution of its maturity [34]. In this regard, when comparing both parameters in the amendments studied, at the final stage, results show evidence of the greater maturity of vermicompost. In any case, both amendments present optimal levels for their use in agriculture as per the parameters found in the literature. [PERSON] et al., 2002 [35], explain that pH values between 6.0-8.5 in the amendments are appropriate for agricultural use, and [PERSON] et al., 2009 [36], suggest that C/N ratio values < 20 indicate maturity. Figure 2: Changes in the temperature and frequency of irrigation and turning in both processes. With regard to electrical conductivity, the final amendment must present values \(<\) 4 dS/m for safe use in agriculture [37; 38]. The mean value of compost was remarkably higher than that of vermicompost. This may be due to the different conditions of humidity of each process, which, in the case of vermicomposting, may have caused a leaching effect (saline lixiviation), given the higher frequency of irrigation. Both electrical conductivity values were similar to, and even lower than in some instances, the ones revealed by other studies for amendments (compost/vermicompost) from urban wastes [39; 40], livestock wastes (hen droppings/manure) [34; 41], and even agricultural wastes such as olive tree pruning byproduct [42]. The macronutrient (NPK) concentrations were higher or similar to those found by other authors in studies of composting and vermicomposting using urban wastes [43], vegetable wastes [44], and agro-industrial wastes [31]. Phytotoxicity is a very useful decisive criterion for assessing whether organic materials are appropriate for agricultural use. Both amendments presented percentages above the minimum value (GI \(<\) 50%) established by [PERSON] et al., 1981 [25], to indicate the absence of phytotoxicity. In both the compost and the vermicompost, the values observed in organic matter (>35%), C/N ratio (<20), and granulometry (<25 mm) were within the limits established by the legislation for agricultural applications and, as per the heavy metals, the total concentrations were under the limits established for the maximum quality category, Class A, pursuant Spanish RD 506/2013 [45]. Finally, the graph in Figure 3 shows the FT-IR spectra of the initial lignocellulosic waste and of the products obtained in each of the processes. As the composting and vermicomposting processes evolve, the matter is transformed due to biodegradation and to polymerization reactions, hence increasing the concentration of organic humic substances. FT-IR can be used to assess the stabilization of organic matter and the quality of the final product [46]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Compost** & **Vermicompost** \\ \hline pH & 6.8 \(\pm\) 0.1 & 7.84 \(\pm\) 0.02 \\ EC (dS-m\({}^{-1}\)) & 4.0 \(\pm\) 0.5 & 1.90 \(\pm\) 0.02 \\ OM (\%) & 64 \(\pm\) 2 & 60.6 \(\pm\) 0.4 \\ N (\%) & 2.1 \(\pm\) 0.4 & 2.2 \(\pm\) 0.3 \\ P (\%) & 0.30 \(\pm\) 0.01 & 0.20 \(\pm\) 0.01 \\ K (\%) & 2.6 \(\pm\) 0.4 & 3.8 \(\pm\) 0.2 \\ C/N & 13.4 & 12.9 \\ GI (\%) & 74.8 & 84.3 \\ Cr (mg/kg) & 26.7 \(\pm\) 0.6 & 24.7 \(\pm\) 0.5 \\ Cu (mg/kg) & 6.1 \(\pm\) 0.1 & 10.5 \(\pm\) 0.3 \\ Ni (mg/kg) & 11.9 \(\pm\) 0.5 & 12.3 \(\pm\) 0.5 \\ Pb (mg/kg) & 16.3 \(\pm\) 0.6 & 15.5 \(\pm\) 0.4 \\ Zn (mg/kg) & 34 \(\pm\) 5 & 27 \(\pm\) 2 \\ Granulometry (mm) & 15.0 * & 15.0 * \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physicochemical characteristics of the compost and vermicompost used. FTIR was applied to reveal how the functional groups changed, comparing the bands in the initial substrate to the ones identified in the organic amendments.