## 4 Discussion  
Despite the high adaptability to different environmental conditions, hop cultivars of European origin are more susceptible to changes in pedo-climatic conditions compared to the American \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Time**} & \multicolumn{2}{c}{**Hallertau Magnum**} & \multicolumn{2}{c}{**Perle**} & \multicolumn{2}{c}{**Spalter Spalt**} \\ \cline{2-7}  & **No Biochar** & **Biochar** & **No Biochar** & **Biochar** & **No Biochar** & **Biochar** \\ \hline T1 & \(7\pm 2\) a & \(8\pm 2\) a & \(8\pm 3\) a & \(6\pm 1\) a & \(8\pm 3\) a & \(5\pm 1\) a \\ T2 & \(8\pm 3\) a & \(9\pm 2\) a & \(9\pm 1\) a & \(7\pm 1\) a & \(8\pm 3\) a & \(7\pm 2\) a \\ T3 & \(9\pm 2\) a & \(10\pm 2\) a & \(10\pm 1\) a & \(8\pm 1\) a & \(9\pm 2\) a & \(8\pm 2\) a \\ T4 & \(15\pm 3\) b & \(15\pm 3\) b & \(11\pm 1\) a & \(12\pm 2\) b & \(11\pm 1\) a & \(12\pm 3\) ab \\ T5 & \(16\pm 2\) b & \(16\pm 4\) b & \(11\pm 1\) a & \(13\pm 4\) b & \(11\pm 1\) a & \(13\pm 3\) b \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Measurements of diameter of shoots (mean \(\pm\) standard deviation) at five different times (T1: 30 June, T2: 18 July, T3: 27 July, T4: 3 November, T5: 21 November). Diameters within columns of each cultivar and treatment followed by different letters (a or b) are significantly different. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Hallertau Magnum**} & \multicolumn{2}{c}{**Perle**} & \multicolumn{2}{c}{**Spalter Spalt**} \\ \cline{2-7}  & **No Biochar** & **Biochar** & **No Biochar** & **Biochar** & **No Biochar** & **Biochar** \\ \hline Number of leaves & \(20\pm 8\) a & \(18\pm 6\) a & \(19\pm 4\) a & \(15\pm 3\) a & \(26\pm 14\) a & \(25\pm 14\) a \\ Bines length (cm) & \(547\pm 55\) a & \(570\pm 30\) a & \(552\pm 27\) a & \(532\pm 61\) a & \(555\pm 94\) a & \(550\pm 75\) a \\ Number of cones & \(97\pm 17\) a & \(144\pm 20\) b & \(84\pm 14\) a & \(123\pm 18\) b & \(75\pm 12\) a & \(106\pm 16\) b \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Measurements of number of leaves (mean \(\pm\) standard deviation) at the beginning of May, and climbing bines length and number of cones at maturity. Statistical differences between treatments (with biochar or without biochar) for each cultivar and parameter are displayed with different letters (a or b). genotypes [27]. Hops require a large amount of water during the growing seasons to optimize yield and quality. Furthermore, soil has to be nutrient-rich, light, well drained, well supplied with moisture, but free from waterlogging, with an optimal pH range between 6.0 and 6.5., although hops also grow on soils with pH from 4.8 to 8.0 [27]. Our study wanted to verify if biochar can positively affect hop growth. As mentioned above, biochar can improve soil water retention, cation exchange capacity, the content of different nutrients, and reduce soil bulk density and N leaching [7]. Moreover, biochar can enhance the uptake of N and other nutrients by improving the root development and the whole plant physiological status [17]. Then, biochar may reduce plant uptake of potentially toxic elements (such as Pb, Cd and As) from soils, due to the adsorption of metals to the negative charges on the surface of biochar particles [35]. However, the efficacy of biochar application depends on various factors concerning both soil and plant. Understanding these factors is essential for maximizing soil productivity and minimizing potential deleterious environmental effects. For example, the positive effect of biochar amendment is more remarkable in a coarse-textured than in a fine-textured soil, and sandy soils are more responsive than clay-rich soils; this positive effect could be also maximized reducing biochar particle sizes in the range of 0.5-1.0 mm [19]. The biomass feedstock could influence the hydraulic properties of biochar: biochar with high porosity and surface area can improve water adsorption [36].