The main objective of the cultivation of energy crops is the production of renewable energy, the substitution of fossil energy resources, and a substantial contribution to energy supply. Thus, energy yield and energy efficiency are the most important criteria for the assessment of energy crops and biomass-based renewable energy chains. Maize is the energy crop with the highest cultivation acreage in Germany because of its high energy yields, but is the subject of controversial debate because of possible detrimental effects on agro-ecosystems. This raises the question as to which energy crops and production systems could be used instead of maize, in order to increase crop diversity and lower environmental impacts. We examined yields, energy inputs, energy outputs, and energy efficiency of alternative energy crops (combinations of catch crops and main crops) compared to maize in four-year field experiments at three southern German sites by means of process analyses. Maize showed moderate energy inputs (11.3–13.2 GJ ha⁻¹), with catch crops ranging from 6.2 to 10.7 GJ ha⁻¹ and main crops ranging from 7.6 to 24.8 GJ ha⁻¹. At all three sites, maize had the highest net energy output compared to the other crops ($\overline{\mathrm{x}}$ = 354–493 GJ ha⁻¹), but was surpassed by combinations of catch and main crops at some sites (winter rye/maize: $\overline{\mathrm{x}}$ = 389–538 GJ ha⁻¹). Although some combinations yielded higher net energy outputs than maize, no other crop or combination of crops outperformed maize regarding energy use efficiency (energy output/energy input: $\overline{\mathrm{x}}$ = 32–45).

中文翻译：

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德国南部田间试验中一年生生物能源作物的能量平衡和能量利用效率

能源作物种植的主要目标是生产可再生能源，替代化石能源，为能源供应做出重大贡献。因此，能源产量和能源效率是评估能源作物和基于生物质的可再生能源链的最重要标准。玉米是德国种植面积最大的能源作物，因为它的能量产量高，但由于可能对农业生态系统产生不利影响，它成为有争议的话题。这就提出了一个问题，即可以使用哪些能源作物和生产系统来代替玉米，以增加作物多样性并降低对环境的影响。我们检查了产量、能量输入、能量输出，通过过程分析，在德国南部三个地点进行的为期四年的田间试验中，替代能源作物（捕获作物和主要作物的组合）与玉米的能源效率进行了比较。玉米表现出中等能量输入（11.3-13.2 GJ ha^-1 )，捕捞作物为 6.2 至 10.7 GJ ha ^-1，主要作物为 7.6 至 24.8 GJ ha ^-1。在所有三个地点，与其他作物相比，玉米的净能量输出最高（$\overline{\mathrm{X}}$= 354–493 GJ ha ^-1），但在某些地点（冬季黑麦/玉米：$\overline{\mathrm{X}}$= 389–538 GJ 公顷^-1 )。尽管某些组合产生的净能量输出高于玉米，但没有其他作物或作物组合在能源使用效率（能量输出/能量输入：$\overline{\mathrm{X}}$ = 32–45）。