## 3 Results
### Effect of Bulk Density and Water Holding Capacity on Cucumber Fruit Yield and Quality  
The number of harvested cucumber fruits grown in lignite substrate and fed with standard EC medium depended on both BD and WHC of the growing mat. The water holding capacity of this substrate was significantly positively correlated with both the total number of harvested cucumber fruits and the number and weight of marketable fruits and non-choice fruits. There was also a significant relationship of bulk density and water capacity of lignite to total cucumber yield (Table 8). The dependence of cucumber fruit number and fruit weight on the physical properties of lignite was confirmed by significant multiple correlation coefficients and the coefficient of determination for cucumber yield in lignite with standard medium EC. In the case of cucumber grown in mineral wool and fed with high EC of nutrient solution, such relationships were not found (Tables 8 and 9). Growing cucumber in lignite substrate only with medium of standard EC proved a significant effect of BD and WHC of this substrate on the number of dropped cucumber fruits. This relationship was shown in the positive linear correlation for both these characteristics of the lignite substrate and in the significance of the multiple correlation coefficient and the coefficient of determination for this treatment, which was 96.47% (Tables 8 and 9). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{**Physical Parameter of the Substrate**} & \multicolumn{5}{c}{**Micronutrient**} \\ \cline{3-6}  & & **Fe** & **Mn** & **Cu** & **Zn** & **B** \\ \hline \multirow{2}{*}{MW/control EC} & BD & \(-\)0.4407 & 0.4478 & 0.0877 & \(-\)0.4108 & 0.4717 \\  & WHC & 0.1183 & 0.4784 & 0.3066 & \(-\)0.0947 & 0.5699 \\ \hline \multirow{2}{*}{L/control EC} & BD & 0.5196 & 0.6525 & 0.5430 & 0.4872 & \(-\)0.2190 \\  & WHC & 0.7998 * & 0.1002 & 0.0863 & 0.0778 & 0.0559 \\ \hline \multirow{2}{*}{MW/high EC} & BD & 0.0233 & \(-\)0.0005 & \(-\)0.5077 & \(-\)0.2007 & 0.3756 \\  & WHC & \(-\)0.5472 & \(-\)0.4904 & \(-\)0.5977 & 0.1155 & 0.5356 \\ \hline \multirow{2}{*}{L/high EC} & BD & 0.0613 & \(-\)0.0184 & \(-\)0.1585 & 0.5994 & \(-\)0.3615 \\  & WHC & \(-\)0.1214 & \(-\)0.2324 & \(-\)0.4497 & 0.8429 * & \(-\)0.2380 \\ \hline \hline \end{tabular}  
* significant at \(p\leq 0.05\).  
\end{table} 
Table 6: Linear correlation coefficient(\({}^{2}\)) for the relationship between micronutrient content in cucumber leaves and physical parameters of the medium (BD, WHC) depending on the type of medium and medium EC. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Micronutrient**} & \multicolumn{2}{c}{**MW/Control EC**} & \multicolumn{2}{c}{**L/Control EC**} & \multicolumn{2}{c}{**MW/High EC**} & \multicolumn{2}{c}{**L/High EC**} \\ \cline{2-7}  & **R** & **D (\%)** & **R** & **D (\%)** & **R** & **D (\%)** & **R** & **D (\%)** \\ \hline \multirow{2}{*}{Fe} & 0.6369 & 40.71 & 0.8004 * & 64.06 & 0.6352 & 40.34 & 0.3144 & 9.88 \\ \hline \multirow{2}{*}{Mn} & 0.5322 & 28.32 & 0.5595 & 31.31 & 0.6783 & 46.01 & 0.3888 & 15.12 \\ \hline \multirow{2}{*}{Cu} & 0.3179 & 10.10 & 0.6480 & 42.00 & 0.5636 & 31.77 & 0.5910 & 34.93 \\ \hline \multirow{2}{*}{Zn} & 0.4337 & 18.81 & 0.3147 & 9.90 & 0.5056 & 25.56 & 0.8614 * & 74.21 \\ \hline \multirow{2}{*}{B} & 0.5521 & 30.48 & 0.6058 & 36.69 & 0.2716 & 7.37 & 0.3780 & 14.29 \\ \hline \hline \end{tabular}  
* significant at \(p\leq 0.05\). D \(<\) 25%—low impact, 25–45%—average impact, 46–100%—high impact.  
\end{table} 
Table 7: Multiple correlation coefficient (R) and coefficient of determination (D) for micronutrient content in cucumber leaves vs. media type and medium EC. A significant relationship was found between cucumber fruit firmness and the physical properties of the medium in hydroponic cultivation (Tables 10 and 11).