Today’s agricultural production is heavily dependent on synthetic nitrogen (N) fertilizer. Its energy-intensive production and use are associated with a number of environmental burdens, such as global warming and marine eutrophication. Furthermore, fertilizer prices are subject to high volatility and have been rising steadily for years. One strategy to reduce the dependence on synthetic N fertilizer is to include legumes in the crop rotation, but it is important that this practice is economically viable to be adopted by farmers. Through gross margin analysis and life cycle assessment (LCA), we quantified the economic and environmental impacts of introducing grain legumes into rainfed bread wheat rotations in northern Spain. The analysis covered the full two-year sequences of barley-wheat, rapeseed-wheat and vetch-wheat. We further investigated the effect of four different bread wheat genotypes on the environmental and economic performance. In this case study, replacing synthetic N fertilizer with legume-fixed N in a two-year cropping rotation decreased most of the analysed environmental impacts. Modelled greenhouse gas emissions were 24 % lower for vetch-wheat compared to barley-wheat and 11 % lower compared to rapeseed-wheat. Despite higher wheat yield, the vetch-wheat rotation had an 18 % lower gross margin than the rapeseed rotation and a 1 % higher gross margin than the barley rotation. The sensitivity analysis showed that only when fertilizer and wheat grain prices were more than doubled, that the legume rotation became more profitable than the other rotations. Consequently, farmers would require a financial incentive to include legumes in crop rotations and reduce environmental impacts.

中文翻译：

---

以豆类为主的轮作作为缓解化肥价格波动的策略？利用生命周期和经济评估对西班牙北部面包小麦基因型进行案例研究


当今的农业生产严重依赖合成氮肥。其能源密集型生产和使用与许多环境负担有关，例如全球变暖和海洋富营养化。此外，化肥价格波动较大，多年来一直稳步上涨。减少对合成氮肥依赖的一项策略是将豆类纳入轮作中，但重要的是这种做法在经济上对农民来说是可行的。通过毛利率分析和生命周期评估（LCA），我们量化了西班牙北部将豆类引入雨养面包小麦轮作的经济和环境影响。该分析涵盖了大麦-小麦、油菜-小麦和野豌豆-小麦的完整两年序列。我们进一步研究了四种不同面包小麦基因型对环境和经济绩效的影响。在本案例研究中，在两年轮作中用豆科植物固氮替代合成氮肥，减少了大部分分析的环境影响。模拟得出的温室气体排放量，与大麦-小麦相比，野豌豆-小麦的温室气体排放量降低了 24%，与油菜籽-小麦相比，温室气体排放量降低了 11%。尽管小麦产量较高，但野豌豆-小麦轮作的毛利率比油菜轮作低 18%，比大麦轮作高 1%。敏感性分析表明，只有当化肥和小麦价格翻一番以上时，豆类轮作才比其他轮作更有利可图。因此，农民需要经济激励才能将豆类纳入轮作并减少对环境的影响。