Impacts of reduced synthetic fertiliser use under current and future climates: Exploration using integrated agroecosystem modelling in the upper River Taw observatory, UK.

The intensification of farming and increased nitrogen fertiliser use, to satisfy the growing population demand, contributed to the extant climate change crisis. Use of synthetic fertilisers in agriculture is a significant source of anthropogenic Greenhouse Gas (GHG) emissions, especially potent nitrous oxide (N2O). To achieve the ambitious policy target for net zero by 2050 in the UK, it is crucial to understand the impacts of potential reductions in fertiliser use on multiple ecosystem services, including crop production, GHG emissions and soil organic carbon (SOC) storge. A novel integrated modelling approach using three established agroecosystem models (SPACSYS, CSM and RothC) was implemented to evaluate the associated impacts of fertiliser reduction (10%, 30% and 50%) under current and projected climate scenarios (RCP2.6, RCP4.5 and RCP8.5) in a study catchment in Southwest England. 48 unique combinations of soil types, climate conditions and fertiliser inputs were evaluated for five major arable crops plus improved grassland. With a 30% reduction in fertiliser inputs, the estimated yield loss under current climate ranged between 11% and 30% for arable crops compared with a 20-24% and 6-22% reduction in N2O and methane emissions, respectively. Biomass was reduced by 10-25% aboveground and by <12% for the root system. Relative to the baseline scenario, soil type dependent reductions in SOC sequestration rates are predicted under future climate with reductions in fertiliser inputs. Losses in SOC were more than doubled under the RCP4.5 scenario. The emissions from energy use, including embedded emissions from fertiliser manufacture, was a significant source (14-48%) for all arable crops and the associated GWP20.

A commentary on key methodological developments related to nutritional life cycle assessment (nLCA) generated throughout a 6-year strategic scientific programme.

Rothamsted Research (RRes) is the world's oldest agricultural research centre, notable for the development of the first synthetic fertilizer (superphosphate) and long-term farming experiments (LTEs) spanning over 170 years. In 2015, RRes recruited several life cycle assessment (LCA) experts and began adopting the method to utilize high resolution agronomical data covering livestock (primarily ruminants), grassland/forage productivity and quality, and arable systems established on its North Wyke Farm Platform (NWFP) and the LTEs. The NWFP is a UK 'National Bioscience Research Infrastructure' (NBRI) developed for informing and testing systems science utilising high-resolution data to determine whether it is possible to produce nutritious food sustainably. Thanks largely to the multidisciplinary knowledge at RRes, and its collaborators, its LCA Team has been at the forefront of methodological advances during a 6-year Institute Strategic Programme (ISP) 'Soil-to-Nutrition' (S2N). While S2N investigated the co-benefits and trade-offs of new mechanistic understanding of efficient nutrient use across scales from pot to landscape, this commentary specifically synthesizes progress in incorporating human nutrition in the context of environmental footprinting, known as 'nutritional LCA' (nLCA). We conclude our commentary with a brief discussion on future pathways of exploration and methodological developments covering various activities along entire agri-food supply-chains.