The reduction of N fertilization in agriculture as part of the Farm to Fork (F2F) strategy plays a central role in the integrated nutrient management action plan of the European Commission. However, the implications of this strategy for mitigating N losses and possible side-effects on grassland yields under global change are largely unknow. We examined how a 20% reduction in N fertilization according to the F2F strategy is likely to impact yields, NO emissions and N leaching of four intensively managed temperate grasslands in the Alpine region, two of them located in Switzerland, the other two in Germany. Following automatic data-driven calibration supported by inverse modeling and a cross-validation step, the process-based model DayCent was used for conducting the analysis. Global change scenarios under the representative concentration pathways (RCPs) 4.5 and 8.5 and a baseline scenario (current climate) were created for the time frame 2041–2060 with the help of the stochastic weather generator LARS-WG. Our results indicated that, under current conditions of climate and CO levels (400 ppm), a 20% decrease in N fertilization would lead to a 5% drop in yields, but also in a 15% decline in NO emissions and a 21% decline in N leaching (largely as NO). Under global change conditions (, climate change and higher atmospheric CO levels), we found that increased yields, mainly induced by higher CO levels, are likely to compensate for yield losses resulting from the reduction in N fertilization. In addition, we found that the effectiveness of the F2F strategy to mitigate N losses is likely to be preserved under global change, still with stronger effect on N leaching. The F2F-induced decline in N losses was stronger when the latter were expressed per unit of harvested dry matter, , up to 17% for NO and up to 42% for N leaching. Although significant, these abatements in N losses are still below the 50% reduction level envisaged by the F2F strategy. Actions related to other axes of the strategy (, sustainable food consumption) will be necessary to further reduce N fertilization and, therefore, to reach this ambitious goal. Our results highlight the usefulness of models in accounting for interacting effects of global change and mitigation practices on multiple ecosystem services of grasslands. They allow quantification of the impact of new policies.

中文翻译：

---

全球变化下欧洲从农场到餐桌战略框架下减少施氮：对高山地区温带草原产量、氧化亚氮排放和氮淋溶的影响


作为“从农场到餐桌”(F2F) 战略的一部分，减少农业施氮量在欧盟委员会的综合养分管理行动计划中发挥着核心作用。然而，这种策略对于减轻全球变化下的氮素损失和可能对草地产量产生的副作用的影响在很大程度上尚不清楚。我们研究了根据 F2F 策略减少 20% 的施氮量可能如何影响阿尔卑斯地区四个集约化管理的温带草原（其中两个位于瑞士，另外两个位于德国）的产量、氮氧化物排放和氮淋溶。在逆向建模和交叉验证步骤支持的自动数据驱动校准之后，使用基于流程的模型 DayCent 进行分析。在随机天气生成器 LARS-WG 的帮助下，创建了 2041-2060 年时间范围内代表性浓度路径 (RCP) 4.5 和 8.5 下的全球变化情景以及基线情景（当前气候）。我们的结果表明，在当前气候和二氧化碳水平（400 ppm）的条件下，施氮量减少 20% 将导致产量下降 5%，同时氮氧化物排放量也会下降 15%，氮氧化物排放量也会下降 21%氮浸出（主要为NO）。在全球变化条件下（气候变化和大气二氧化碳浓度升高），我们发现，主要由二氧化碳浓度升高引起的产量增加可能会弥补施氮量减少造成的产量损失。此外，我们发现，F2F 策略减轻氮素损失的有效性很可能在全球变化下得以保留，但对氮素淋失仍具有更强的影响。 当后者以每单位收获干物质表示时，F2F 诱导的氮损失下降更为强烈，NO 高达 17%，N 浸出高达 42%。虽然氮素损失的减少幅度很大，但仍低于 F2F 策略设想的 50% 减少水平。为了进一步减少施氮量，从而实现这一雄心勃勃的目标，需要采取与该战略其他轴心（可持续粮食消费）相关的行动。我们的结果强调了模型在解释全球变化和减缓实践对草原多种生态系统服务的相互作用影响方面的有用性。它们可以量化新政策的影响。