Silage maize and sugar beet for biogas production in rotations and continuous cultivation: dry matter and estimated methane yield
Since silage maize is the main crop grown for biogas production (biomass crop) in Germany; its increasing cultivation is critically discussed in terms of social and agronomical aspects. To investigate if sugar beet is suitable as an alternative biomass crop to silage maize; three-year field trials with both biomass crops in rotations with winter wheat (food crop) and continuous cultivation were conducted at three highly productive sites. Dry matter (DM) yield per hectare was measured via field trials whereas methane yield per hectare was estimated via a calculation. Higher annual DM yield was achieved by silage maize (19.5–27.4 t/ha/a) compared to sugar beet root (10.7–23.0 t/ha/a). Dry matter yield was found to be the main driver for the estimated methane yield. Thus; higher estimated methane yield was produced by silage maize (6458–9388 Nm3/ha) with overlaps to sugar beet root (3729–7964 Nm3/ha). We; therefore; classify sugar beet as a suitable alternative biomass crop to silage maize; especially when cultivated in crop rotations with winter wheat. Additionally; we found that the evaluation of entire crop rotations compared to single crops is a more precise approach since it includes rotational effects.