Socioeconomic barriers of nitrogen management for agricultural and environmental sustainability

Synthetic nitrogen (N) fertilizers support global food production and feed over half of the global population. However, more than half of the N fertilizers applied to croplands are not absorbed by crops, but lost to the environment, leading to low N use efficiency (NUE) globally. Identifying and overcoming socioeconomic barriers to achieve an improvement of NUE and a reduction in N loss is thus key for N management and to attain agricultural and environmental sustainability. In this paper, we compiled the global cropland N budgets at a national scale (1961-2018) and developed robust econometric models to explore the relationship between cropland N use with socioeconomic factors. The results demonstrate that economic development and farm size are the key drivers to improve NUE for agricultural and environmental sustainability. In less developed countries, it is difficult for farmers to access chemical fertilizers, leading to croplands receiving too little N input and at a high NUE, but suffering from soil N depletion. As economic development progresses, more fertilizer is produced and applied, but smallholder farming typically leads to over-fertilization and consequently N losses to the environment. Large-scale farming improves NUE, reduces N loss and benefits agricultural production and environmental protection. Also, interactions between farm size and economic development, international trade, crop and livestock systems, and related policies are important causes for changes in the NUE of the whole agricultural system. Overcoming these socioeconomic barriers especially combining large-scale farming could effectively reduce excessive N inputs and sustain agricultural and environmental N management, while maintaining food production, resulting in a triple-win for food security, poverty alleviation, and environmental protection.