As the world’s rising population faces increasing challenges of food insecurity, land scarcity, soil degradation, and environmental pollution induced by nitrogen-based fertilisers, there is an urgent need to identify more sustainable and viable farming practices.
Atmospheric scientist Dr Amos Tai (Croucher Fellowship 2012), of The Chinese University of Hong Kong, teamed up with life scientists to explore the use of intercropping as a farming technique to replace traditional monoculture, which has various adverse environmental impacts including air pollution and smog caused by ammonia released from farms.
Intercropping refers to the growing of two or more crop types in one field. However, this farming practice requires more costly machinery and labour than monoculture, which has in turn resulted in a low adoption rate in rural communities in China.
The scientists used a combination of advanced computer models to find that intercropping would increase crop productivity and require less synthetic fertilisers, which in turn would reduce ammonia emitted and the resulting air pollutants caused by the excessive use of such fertilisers. The findings have been published in Environmental Research Letters.
The team made use of data from the field experiments conducted by a collaborator at Sichuan Agricultural University, China to improve the DeNitrification-DeComposition (DNDC) computer model, and used it to compare the intercropping and monoculture of maize and soybean in terms of their simulated crop yield, amount of fertiliser use, and ammonia emitted.
Using the computer model, the team predicted what would happen if such a maize (non-legume)-soybean (legume) intercropping system were adopted in all maize and soybean croplands across every Chinese province. The results showed that on land originally designated for maize or soybean production only, intercropping could not only produce the same quantity of maize (4,300-16,000 kg per hectare), but an additional batch of soybean (2,800-5,000 kg per hectare). Moreover, 42% less fertiliser would be required, and 45% less ammonia emitted.
The team fed these results into GEOS-Chem, an atmospheric chemistry model, to compute how such a reduction in ammonia would affect the formation of fine particulate matters in China. The model predicted that the average annual pollutant concentration could be lowered by up to 1.5 micrograms per cubic metre (2.3 per cent), and the improved air quality would be most significant in East and Northeast China.
The study concluded with a cost-benefit analysis of maize-soybean intercropping against the current monocultural farming practice for the two crops. Although additional labour and machinery might double the costs, the nationwide use of intercropping could increase the annual national income by US$67 billion, including US$59 billion from increased crop sales, and US$13 billion saved from air pollution-related public health expenses.
Dr. Tai said that the study showed that large-scale adoption of intercropping could benefit the Chinese economy, environment, and people’s health. “We hope this work can help demonstrate the use of a scientific framework to assist policymakers, governments, and other organisations around the globe in evaluating the potential of various sustainable farming methods, and to efficiently allocate their resources to alleviate environmental and food supply issues in the foreseeable future.”
Dr. Amos P. K. Tai is an Associate Professor in the Earth System Science Programme in the Faculty of Science at The Chinese University of Hong Kong. He received a Croucher Fellowship in 2012 to support postdoctoral research in the Department of Civil and Environmental Engineering at MIT on the impacts of climate change and air pollution on global food security.
- Dr Tai’s personal page (The Chinese University of Hong Kong):https://www.cuhk.edu.hk/sci/essc/people/tai_pk-Amos.html
- Dr Tai’s personal page (Croucher Foundation): https://scholars.croucher.org.hk/scholars/amos-p-k-tai
- The scientific paper Dr Tai published in Environmental Research Letters in 2019: https://iopscience.iop.org/article/10.1088/1748-9326/aafc8b
- Press release of The Chinese University of Hong Kong: https://www.cpr.cuhk.edu.hk/en/press_detail.php?id=3032