This book is a synthesis of contributions drawn from the 12th Nitrogen Workshop held at the University of Exeter, UK. It provides a valuable compilation of current research, aimed at reconciling the environmental and economic components of N cycling within the context of a productive agricultural industry. The book is divided into seven main sections, which examine systematically, the nature of the problems associated with losses of N and a range of possible solutions. Section 1, 'Drivers towards sustainability-why change?' identifies the need to adopt new strategies to avoid losses to the environment. Section 2 considers the options for 'Matching supply with demand', followed by the reasons for, and means of 'Controlling losses to air' and to 'water' in section 3 and 4. Section 5 describes the challenges of 'Reconciling productivity with environmental considerations'. The remaining sections describe some mathematical models to assist the researcher, with the final section devoted to reports from the 'Themed Working Groups' which debated the following topical questions: Organic matter: does it matter, or can technology overcome most problems related to soil fertility? Optimising N additions: can we integrate fertilizer use and manure use? Controlling gaseous N emissions: what is achievable? Missing N: is the solution in dissolved N? Pollution problems: mitigation, or are we swapping one form of pollution for another? System studies: do we need them, or can they be replaced by desktop studies? Model answers: can we improve their level of confidence and applicability? This book will be of value to researchers, policy makers and all those wishing to promote more efficient use of N.