## 3 Results
### Grape Composition
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Variable** & **Treatment** & **2013** & **2014** & **2015** & **2016** & **Average 2013–2016** \\ \hline \multirow{4}{*}{TTSS (\({}^{\circ}\)Brix)} & K15 & 15.3 & 14.8 & 18.0 & 17.7 & 16.5 \\  & K30 & 15.5 & 15.1 & 18.1 & 17.7 & 16.6 \\  & K60 & 15.0 & 14.6 & 18.1 & 17.3 & 16.3 \\  & K0 & 15.8 & 15.0 & 18.1 & 17.8 & 16.7 \\  & F test sign & ns & ns & ns & ns & ns \\  & Treatment \(\times\) year & & & & & ns \\ \hline \multirow{4}{*}{Titratable acidity (g/L)} & K15 & 7.9 & 9.6 & 5.4 & 6.6 & 7.4 & b \\  & K30 & 7.8 & 10.0 & 5.8 & 6.9 & 7.6 & ab \\  & K60 & 8.3 & 10.1 & 6.1 & 7.0 & 7.9 & a \\  & K0 & 7.7 & 9.5 & 5.8 & 6.4 & 7.4 & b \\  & F test sign & ns & ns & ns & ns & ** \\  & Treatment \(\times\) year & & & & & ns & \\ \hline \multirow{4}{*}{pH} & K15 & 3.18 & 3.13 & ab & 3.39 & 3.23 & 3.23 \\  & K30 & 3.18 & 3.10 & b & 3.38 & 3.23 & 3.22 \\  & K60 & 3.16 & 3.14 & a & 3.36 & 3.24 & 3.23 \\  & K0 & 3.19 & 3.11 & ab & 3.37 & 3.22 & 3.22 \\  & F test sign & ns & \({}^{*}\) & ns & ns & ns & \\  & Treatment \(\times\) year & & & & & ns & \\ \hline \multirow{4}{*}{Malic acid (g/L)} & K15 & 4.6 & ab & 5.7 & b & 2.8 & b & 3.2 & b & 4.1 & b \\  & K30 & 4.4 & b & 6.4 & a & 2.8 & b & 3.5 & ab & 4.3 & ab \\  & K60 & 5.1 & a & 6.5 & a & 3.3 & a & 3.7 & a & 4.7 & a \\  & K0 & 4.3 & b & 6.0 & ab & 2.9 & ab & 3.1 & b & 4.1 & b \\  & F test sign & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & \({}^{**}\) & \({}^{**}\) & \({}^{**}\) & \({}^{**}\) \\  & Treatment \(\times\) year & & & & & & & ns & \\ \hline \multirow{4}{*}{Tartaric acid (g/L)} & K15 & 6.0 & c & 6.2 & a & 4.5 & 7.3 & b & 6.0 & b \\  & K30 & 6.4 & ab & 6.5 & a & 4.6 & 7.2 & b & 6.2 & ab \\  & K60 & 6.6 & a & 6.2 & a & 4.8 & 7.8 & a & 6.4 & a \\  & K0 & 6.1 & bc & 5.8 & b & 4.7 & 6.9 & b & 5.9 & b \\  & F test sign & \({}^{*}\) & \({}^{*}\) & \({}^{*}\) & ns & \({}^{*}\) & \({}^{**}\) & \({}^{**}\) & \({}^{**}\) \\  & Treatment \(\times\) year & & & & & & ns & \\ \hline \multirow{4}{*}{Potassium (mg/L)} & K15 & 1144 & 1215 & 1184 & ab & 1196 & 1185 & ab \\  & K30 & 1165 & 1301 & 1320 & bc & 1270 & 1264 & a \\ \cline{1-1}  & K60 & 1152 & 1265 & 1391 & a & 1192 & 1250 & a \\ \cline{1-1}  & K0 & 1075 & 1197 & 1152 & c & 1178 & 1151 & b \\ \cline{1-1}  & F test sign & ns & ns & \({}^{*}\) & ns & \({}^{**}\) & \({}^{**}\) & \({}^{**}\) \\ \cline{1-1}  & Treatment \(\times\) year & & & & & & ns & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fruit composition of Glera vines in response to different K supply treatments. Means followed by different letters differ significantly by [PERSON]’s least significant difference test (\({}^{*}\), \({}^{**}\), \({}^{**}\) = \(p\)\(\leq\) 0.05, 0.01, 0.001, respectively; ns: non-significant). To further analyze the relation between K content and the pH in the berry, a regression was calculated using the data collected in the four years of study (Figure 4). Weak correlations between K content and pH were found only in 2013 (R = 0.49, \(p\) = 0.014) and in 2016 (R = 0.54, \(p\) = 0.0066) vintages, but on the averaged data, no significant relations were found between these two parameters (R = 0.19, \(p\) = 0.063). Figure 4: The relation between grape juice pH and K concentration for Glera vines over 4 study seasons. Within each year, a data point represents the means of 6 replicate vines for every treatment. The dotted line represents the mean regression line for all vintages. Figure 3: Trends for tittatable acidity, during the ripening period, in response to different potassium supply. Data are means \(\pm\) SE. Significant differences are indicated by * = \(p\) < 0.05, as attested by [PERSON]’s test.