The Second International Symposium on Magnesium was held in São Paulo, Brazil, in November 2014. An overview of the role of magnesium in food production was the theme of the opening session of that meeting. This paper considers agricultural production systems, mainly in terms of sustainability, fertiliser-use efficiency and food security, with emphasis on soils of tropical regions. Magnesium in soils and plants, as well as in relation to other nutrients and to other agricultural production factors, is especially covered. Finally, the role of magnesium is considered in terms of plant and animal health, nutrient management and the need of future research.