In order to reduce water pollution by nitrates as required by EC directives, it is important to improve understanding of relationships between N inputs, management practices and nitrate losses to watercourses. This study will use currently available models and experimental relationships to determine integrated effects of management on flows and losses of nitrate and other forms of N in various options for animal production farming systems. Such options will include fertilizer adjustments which make best use of N in the soil profile, novel strategies for fertilizer management using grass/clover, replacement of grass silage with maize silage, various slurry treatments and combinations of these. Impacts of alternative managements which aim to increase N use efficiency and reduce nitrate leaching on an annual basis will be examined using a case study dairy farm as well as modelling techniques. The study will provide predictions of the following: N inputs from all known sources and associated changes that will occur as a result of adoption of new management procedures; removal of N in meat/milk or other commodities from the farm; nitrate leaching, ammonia volatilisation and denitrification; internal recycling of N in plant, soil, feeds and wastes; and economic costs/benefits of proposed changes to the farmer. The approach adopted in this study will then be extended to other livestock systems (e.g. beef cattle), as well as a range of other soil types and environments. In addition, a simple economic assessment of financial and energy use implications of the suggested management options will performed. This will evaluate direct implications for dairy gross margins of outputs and resource use changes flowing from different N regimes. Furthermore, N input/output balances of a wide range of farming enterprises will be performed, using questionnaire and interview approaches, to determine "excess" N (i.e. inputs minus removal in products) on each farm. Relationships will be sought between "excess" N and N use efficiency, livestock production type, intensity, soil and management characteristics. Finally, information from model and survey approaches will be collated and key features will be identified which will permit practical on-farm progress and pinpoint research needs for the future.