Modelling and Assessing the Impacts of Intercropping, as a Sustainable Farming Practice, on Food Security, Air Quality, and Public Health – Ka Ming Fung, Graduate Division of Earth and Atmospheric Sciences, The Chinese University of Hong Kong

May 10, 2019 @ 11:00 am – 12:15 pm
Pfizer Lecture Theatre
Department of Chemistry
Paul Griffiths

Agriculture is the major emitter of atmospheric ammonia (NH3) in Europe, China, and the US (85 – 95%). This NH3 is also attributable to approximately 20% of the fine particulate matter (PM2.5) formed, which harms human health in the neighbourhood areas. The fast-growing food production, due to the rising world population and their more meat-inclined dietary habits, could thus worsen the pollution problem. Previous field studies have shown that soybean intercropping can exploit the mutualistic interactions between crops to promote legume nitrogen fixation for enhancing crop yield, reducing fertiliser use, and thus diminishing NH3 emission. In this study, we aim to investigate the potential benefit of large-scale intercropping on crop productivity, air quality, and public health. To quantify crop yield and NH3 emission under intercropping, we implement into a soil biogeochemical model, DeNitrification-DeComposition (DNDC), a new scheme to parametrize the belowground interactions of intercropped crops. With the DNDC-simulated NH3 emission, we predict the formation of downwind PM2.5 using a global 3-D chemical transport model, GEOS-Chem. We find that, if all Chinese farms are adopting maize-soybean intercropping, the same croplands which were initially for only maize or soybean can now produce both crops with comparable yields (90-100%) as their monoculture counterparts. The fertiliser use for intercropping is 42% lower, leading to a reduction in NH3 emission by 45% and a drop in PM2.5 concentration by up to 2.3% (equivalent to 1.5 μg m-3). This improvement can spare the Chinese government US$13 billion per year in air pollution-related health damage costs. Toward a better understanding on how regional conversion to sustainable farming alternatives may affect global climate and air quality, we are developing a process-based NH3 volatilisation scheme and the parametrisation of crop-crop belowground interactions into the Community Earth System Model (CESM). We hope that our study can help policymakers to evaluate the costs and benefits of adopting sustainable alternatives and derive a science-based long-term strategy for food security and air pollution mitigation.