21EJP SOIL: CropGas: The effect of conservation agriculture interventions on greenhouse gas emissions

面对气候变化，农业必须以可持续方式确保所有人的粮食安全。人们担心耕作对土壤质量（结构稳定性、土壤有机碳、生物功能的损失）和温室气体（GHG）排放的影响。IPCC最近的报告（第3工作组）将农业和土地利用变化确定为与能源部门相当的人为温室气体来源，具有相当大的缓解空间。从北半球的集约化温带系统到南半球的小农和自给生产，人们对保护性农业（CA）如何提高作物的可持续性产生了广泛的兴趣。总而言之，免耕或少耕（ZMT）是为了减少对土壤结构的破坏。有机残留物的保留，或其他建立土壤有机碳（SOC）的手段，以及通过轮作或间作实现种植系统的多样化，都是CA的组成部分。虽然有证据表明CA可以提高作物产量对气候变化的适应能力，改善土壤结构，但其对温室气体收支的影响问题仍未解决。特别是，不同的温室气体可能对耕作方式的变化和有机碳状态的增加有不同的响应，因此，考虑到不同气体对气候影响的差异，需要一个强有力的证据基础来评估温室气体收支各组成部分之间的权衡，以及对全球变暖潜势（GWP）的净效应。该项目汇集了来自欧洲和撒哈拉以南非洲（SSA）的研究人员，他们一直活跃于农业生产和温室气体研究，为农业生产实践对农业土壤温室气体预算影响的证据基础做出实质性贡献。证据将跨越温带欧洲系统和非洲系统，包括小农生产。我们将使用英国、爱尔兰和波兰已建立的实验，其中包括当地相关的ZMT和作物轮作干预与传统种植的比较。同样，南非、赞比亚、津巴布韦和马拉维的现有实验也将被使用。最后三个站点是现有网络（CEPHaS，还包括RR， BGS和UoN）的一部分，旨在将传统管理与ZMT和残留物保留结合其他CA干预措施进行比较。我们将安装最先进的现场仪器来测量各个试验点的土壤温室气体排放和土壤变量。这将提供精细尺度时间分辨率的测量。我们将制定可靠的统计分析方法，并训练每个实验组如何使用这些方法。这些结果将使我们能够评估当地环境和作物管理如何影响土壤温室气体排放中CO2、CH4和N2O的相对重要性，以及CA的采用是否会减轻这些排放的GWP。排放的测量将与作物产量和其他可持续性指标一起进行评估，从而对系统中的权衡进行更广泛的评估。在可能的情况下，将利用数据得出具体国家的排放系数。我们将通过过程模型评估对实验处理中观察到的差异的预测，特别是是否有必要明确说明控制排放的物理和生物地球化学过程如何受到土壤结构的影响，我们将通过x射线计算机断层扫描对其进行量化。实际上，这将显示预测模型所需的详细程度。它还将有助于确定管理-土壤相互作用中决定温室气体产生的关键过程。为了将我们的分析背景化，我们将回顾与CA下温室气体通量相关的文献，并对所回顾的研究进行荟萃分析。这将使我们能够进一步评估CA在缓解战略中的潜在作用，并评估系统中的各种权衡。

Agriculture must ensure food security for all, sustainably and in the face of climate change. There is concern about the impact of farming on soil quality (losses of structural stability, soil organic carbon, biological functions), and greenhouse gas (GHG) emissions. The most recent IPCC report (Working Group 3) identified agriculture and land use change as a comparable source of anthropogenic GHG to the energy sector, with considerable scope for mitigation.There is widespread interest in how conservation agriculture (CA) might increase the sustainability of cropping, ranging from intensive temperate systems in the global north to smallholder and subsistence production in the global south. In all, zero or minimum tillage (ZMT) is implemented to reduce the disruption of soil structure. The retention of organic residues, or other means to build soil organic carbon (SOC), and the diversification of cropping systems through rotations or intercropping are all components of CA. While there is evidence that CA can increase the resilience of crop yields to climate variations and improve the structure of soils, the question of its impact on GHG budgets remains open. In particular, it is likely that different GHGs respond differently to changes in tillage practice and increase in SOC status, so a strong evidence base is needed to assess the trade-offs between components of the GHG budget under CA, and the net effect on global warming potential (GWP), given differences in the climate impact of different gases.This project brings together researchers from Europe and sub-Saharan Africa (SSA) who have been active in CA and GHG research to make a substantive contribution to the evidence base for the impact of CA practices on GHG budgets for agricultural soils. The evidence will span both temperate European systems, and systems in SSA, including smallholder production.We will use established experiments in the UK, Ireland, and Poland that include locally relevant ZMT and crop rotation interventions with conventional cultivation comparisons. Similarly, existing experiments in South Africa, Zambia, Zimbabwe and Malawi will be used. The last three sites are part of an existing network (CEPHaS, also including RR, BGS and UoN) designed to compare conventional management with ZMT and residue retention combined with other CA interventions.We shall install state-of-the art field instrumentation to measure soil GHG emissions and soil variables for plots across the experimental sites. This will provide measurements at fine-scale temporal resolution. We shall develop robust methods for statistical analysis and train each of the experimental groups in their use. The results will allow us to evaluate how local environment and crop management affect the relative importance of CO2, CH4 and N2O in GHG emissions from soil, and whether adoption of CA mitigates the GWP of these emissions.Measurements of emissions will be appraised alongside crop yield and other sustainability metrics allowing the wider assessment of tradeoffs in the systems. Where possible, data will be used to derive country specific emissions factors.We shall evaluate the prediction of observed differences in our experimental treatments by process models, and in particular whether it is necessary to account explicitly for how the physical and biogeochemical processes controlling emissions are affected by soil structure, which we will quantify by x-ray computerized tomography. Practically this will show the level of detail required in predictive models. It will also help to identify the key processes in the management-soil interaction which determine GHG production.To contextualise our analyses, we shall review the literature relating to GHG fluxes under CA and undertake a meta-analysis of reviewed studies. This will allow us to evaluate further the potential role of CA in mitigation strategies and assess various trade-offs in the system.