Department of Energy and Technology, Swedish University of Agricultural Sciences (SLU), SE-750 07 Uppsala, Sweden.
Department of Biosystems and Technology, Swedish University of Agricultural Sciences (SLU), SE-234 22 Lomma, Sweden.
Sci Total Environ. 2024 Mar 25;918:170629. doi: 10.1016/j.scitotenv.2024.170629. Epub 2024 Feb 4.
Cover crop cultivation can be a vital strategy for mitigating climate change in agriculture, by increasing soil carbon stocks and resource efficiency within the cropping system. Another mitigation option is to harvest the cover crop and use the biomass to replace greenhouse gas-intensive products, such as fossil fuels. Harvesting cover crop biomass could also reduce the risk of elevated NO emissions associated with cover crop cultivation under certain conditions, which would offset much of the mitigation potential. However, harvesting cover crops also reduces soil carbon sequestration potential, as biomass is removed from the field, and cultivation of cover crops requires additional field operations that generate greenhouse gas emissions. To explore these synergies and trade-offs, this study investigated the life cycle climate effect of cultivating an oilseed radish cover crop under different management strategies in southern Scandinavia. Three alternative scenarios (Incorporation of biomass into soil; Mowing and harvesting aboveground biomass; Uprooting and harvesting above- and belowground biomass) were compared with a reference scenario with no cover crop. Harvested biomass in the Mowing and Uprooting scenarios was assumed to be transported to a biogas plant for conversion to upgraded biogas, with the digestate returned to the field as an organic fertiliser for the subsequent crop. The climate change mitigation potential of cover crop cultivation was found to be 0.056, 0.58 and 0.93 Mg CO-eq ha in the Incorporation, Mowing and Uprooting scenario, respectively. The Incorporation scenario resulted in the highest soil carbon sequestration, but also the greatest soil NO emissions. Substitution of fossil diesel showed considerable mitigation potential, especially in the Uprooting scenario, where biogas production was highest. Sensitivity analysis revealed a strong impact of time of cover crop establishment, with earlier establishment leading to greater biomass production and thus greater mitigation potential.
种植覆盖作物是农业缓解气候变化的重要策略，可以增加土壤碳储量和作物系统内的资源效率。另一种缓解措施是收获覆盖作物的生物质，并用其替代温室气体密集型产品，如化石燃料。在某些条件下，收获覆盖作物的生物质还可以降低与覆盖作物种植相关的氮氧化物排放风险，从而抵消部分缓解潜力。然而，收获覆盖作物也会减少土壤碳封存潜力，因为生物质被从田间移除，而且种植覆盖作物需要额外的田间作业，这些作业会产生温室气体排放。为了探讨这些协同作用和权衡取舍，本研究调查了在南斯堪的纳维亚不同管理策略下种植油料萝卜覆盖作物的生命周期气候效应。与无覆盖作物的参考情景相比，三种替代情景（生物质纳入土壤；刈割地上生物质；拔出地上和地下生物质）被进行了比较。假设在刈割和拔出情景中收获的生物质被运往沼气厂转化为升级沼气，消化物作为有机肥料返回田间，用于后续作物。研究发现，在纳入、刈割和拔出情景中，覆盖作物种植的气候变化缓解潜力分别为 0.056、0.58 和 0.93 Mg CO-eq ha。纳入情景导致了最高的土壤碳封存，但也导致了最大的土壤氮氧化物排放。替代化石柴油显示出相当大的缓解潜力，特别是在沼气产量最高的拔出情景中。敏感性分析表明，覆盖作物建立时间的影响很大，早期建立会导致更多的生物质生产，从而产生更大的缓解潜力。
