Global nitrogen pollution from cropping could be cut substantially through farm size optimization amid socio-economic drivers

Abstract

Abstract Mitigating nitrogen pollution in regions dominated by smallholder farming is crucial for achieving Sustainable Development Goals (SDGs) while feeding the growing population. Small farms with size less than two hectares, constituting around 84% of all farms globally, support food production but suffer from low nitrogen use efficiency and nitrogen overuse. It remains poorly understood where to put forward future efforts in small farms to address both production and pollution challenges simultaneously. By linking agronomic research with air quality modelling, health impact as well as cost-benefit analysis, here we report the outcome of a global integrated analysis focused on enhancing nitrogen use efficiency and environmental performance by optimizing small farms. Our findings reveal that small farms, less than 2 hectares in size, apply nitrogen at a rate 2-3 times higher than large farms for major crops. The overall global nitrogen waste amounts to approximately 103 billion USD in 2020, with a significant portion in Asia (65%), followed by the Americas (15%), Africa (11%), Europe (8%), and Oceania (1%). Through optimizing small farms with consolidating fragmented lands in alignment with socio-economic drivers, we predict that substantial nitrogen use efficiency improvement can be achieved by 2-14%; this could potentially cut global nitrogen waste in half (13-71% across regions) and avoid over 142,000 premature deaths per year and generate an annual benefit of over 500 billion USD globally. Although significant investment is required for this shift, there would be substantial progress towards achieving SDGs, associated with food security and human health.