# Assessment of Areal Methane Yields from Energy Crops in Ukraine, Best Practices
## 3 Results and Discussion
### Maize  
Five varieties of maize (_Zea mays L_.) were analysed: \"Vatta MV\" (FAO 280), \"Shedevr MV\" (FAO 320), \"Slobozhans'kyi MV\" (FAO 290), \"Svitanok MV\" (FAO 250) and \"Kardynal MV\" (FAO 280). The selected varieties represented a wide ripeness spectrum (FAO 250-320). While \"Varta MV\" and \"Shedevr MV\" are especially recommended for steppe zones, the variety \"Slobozhans'kyi MV\" is preferably grown on humid sites and the varieties \"Svitanok MV\" and \"Kardynal MV\" grow best in the steppe, forest-steppe and marshlands covered with shrubs known as \"Polesia\". According to literature, the highest methane yields for maize can be obtained when harvesting it in the vegetation stage of milk to wax ripeness (BBCH-codes 73-85) [12; 23]. However, the timing of these vegetation stages depends on the crop variety and weather conditions. The values of DMFM, VSDM, DMY and crop N uptake are provided in Table 3; the SMY, AMY and BBCH-codes of the maize samples are given in Figure 2.  
According to the research results for all the maize varieties, the samples harvested at H3 harvesting time (BBCH-codes 87-89) had the highest average values of DMFM (42.68 \(\pm\) 7.44%), VSDM \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Cultivar** & **Harvesting Time** & **DMM\({}^{*}\),[\%]** & **VSDM\({}^{**}\), [\%]** & **DMY\({}^{***}\), & **Crop N Uptake,** \\  & & & & **[tDMM ha\({}^{-1}\)]** & **IkgN ha\({}^{-1}\)]** \\ \hline Kardynal MV & H1 & 24.4 (1.10) & 93.9 (4.22) & 7.30 (0.33) & 55.45 (2.46) \\ Shedevr MV & H1 & 25.0 (1.13) & 93.2 (4.19) & 7.0 (0.35) & 87.8 (3.95) \\ Slobozhans’Kyi MV & H1 & 27.7 (1.25) & 93.4 (4.20) & 71.0 (0.46) & 71.0 (3.19) \\ Svitanok MV & H1 & 24.3 (1.09) & 93.7 (4.22) & 9.75 (0.44) & 116.9 (5.26) \\ Vura MV & H1 & 26.9 (1.21) & 94.3 (4.25) & 8.91 (0.40) & 76.6 (3.49) \\ Kardinal MV & H2 & 25.8 (0.52) & 96.5 (1.93) & 7.71 (0.15) & 58.63 (1.17) \\ Shedevr MV & H2 & 27.4 (0.58) & 96.1 (1.92) & 8.44 (0.17) & 96.2 (1.92) \\ Slobozhans’Kyi MV & H2 & 36.9 (0.74) & 96.1 (1.92) & 13.5 (0.27) & 94.6 (1.89) \\ Svitanok MV & H2 & 25.6 (0.51) & 81.3 (1.63) & 10.3 (0.21) & 123.24 (2.47) \\ Vura MV & H2 & 35.4 (0.71) & 96.9 (1.94) & 11.7 (0.23) & 100.8 (2.02) \\ Kardinal MV & H3 & 39.4 (1.10) & 95.4 (2.67) & 11.78 (0.33) & 89.5 (2.51) \\ Shedevr MV & H3 & 32.2 (0.90) & 95.7 (2.68) & 9.91 (0.28) & 113.0 (3.17) \\ Slobozhans’Kyi MV & H3 & 45.6 (1.28) & 95.9 (2.69) & 16.7 (0.47) & 116.8 (3.27) \\ Svitanok MV & H3 & 44.0 (1.23) & 97.3 (2.72) & 17.7 (0.49) & 211.8 (5.93) \\ Vata MV & H3 & 52.2 (1.46) & 97.2 (2.72) & 17.3 (0.48) & 148.7 (4.16) \\ \hline \hline \end{tabular}  
* The dry matter content related to fresh matter, ** Volatile solids content related to dry matter, *** Dry matter yield.  
\end{table} 
Table 3: Maize: DM and VS- content at harvest time, dry matter yield per hectare and N-uptake. Units are given in square brackets. Values are given as mean; standard deviation is given in round brackets. Figure 2: Specific methane yield (SMY) and areal methane yield (AMY) of the maize varieties harvested at H1, H2 and H3 harvesting times, which correspond to a certain BBCH-code related to a specific stage of crop phenological development. Histograms are charted based on the mean values; error bars indicate the variability between the three replications. Lower case letters indicate significant differences between all the maize samples according to the results of the Tukey test. (96.30 \(\pm\) 0.86%), DMY (14.67 \(\pm\) 3.56 t\({}_{\rm DM}\) ha\({}^{-1}\)), crop N uptake (135.98 \(\pm\) 47.34 kg\({}_{\rm N}\) ha\({}^{-1}\)) and AMY (4929.99 \(\pm\) 1285.53 m\({}^{3}\) ha\({}^{-1}\)). However, the highest average values of SMY (0.35 \(\pm\) 0.03 m\({}^{3}\) kg\({}^{-1}\)VS) were measured for the maize samples harvested at H2 harvesting time (BBCH-codes 83-85).