There is widespread public concern about the effects of nitrate derived from farming on water quality and public health. But research on nitrate during the past decade has revealed wide discrepancies between public perceptions and reality. The main problems from nitrate are ecological changes in coastal and estuarine waters and nitrous oxide in the atmosphere. This gas, largely derived from nitrate, is a threat to the ozone layer in the stratosphere and is also a greenhouse gas. This book builds on "Farming, Fertilizers and the Nitrate Problem" (CABI, 1991) by Addiscott, Whitmore and Powlson but has been restructured to take account of new developments and to bring out more clearly the role of politicians and economists in the "nitrate problem."