Managing nitrogen on the farm: the devil is in the detail

Agricultural activity is a major source of nitrate in surface and ground waters. There has been a large research effort over the last 20 years to understand nitrate leaching processes and to develop ‘best management practices’ (BMPs) that can be adopted in farming systems to reduce losses to the wider environment. This paper reviews some of the issues relating to the development, use and adoption of these BMPs in farming systems. There is significant evidence from farming systems experiments and modelling studies that combinations of BMPs can decrease nitrate losses from agricultural land, though nothing is foolproof (the weather plays a key role in determining success). The challenges are greater in some regions (dry climate, ‘leaky’ soils) and in some enterprises (intensive animal farming systems). The adoption of BMPs on farms requires attention to detail and a high level of management skill, so providing advisory support to farmers is essential. Even with the progress that has been made in recent years, there is still work to do. This includes encouraging uptake on farms and dealing with potential conflicts between BMPs when they create ‘pollution swapping’ or where there is potential for a large economic penalty for the farmer. We also suggest that there is a need for more innovation in developing BMPs and a need to recognise that, in some situations, radical changes to farming systems may be the only solution.