This booklet focuses on the use, effects and management of two key nutrients - nitrogen and phosphorous. Together they play an important role in the global and local sustainable development agendas. On the one hand, their production and use means higher levels of crop production and food security. On the other hand, their excess use and production, the result of a range of important human activities, leads to severe pollution of air, water, land and sea around the world. The present result is an apparent divide between societal needs for food and energy and a complex web of adverse environmental impacts, which undermine ecosystems and the services, and livelihoods they provide. This conundrum is set to intensify, to the cost of countries as demand for food and energy increase and the levels of demand for nitrogen and phosphorous grow.