| | | 3.1 Introduction |
During the first two to three decades after the second world war, most countries encouraged their agricultural sector to increase the production quantities and to decrease the production costs so that the consumers could benefit from lower prices on agricultural produces. However, this could only be achieved by more intensive production, e.g. by tremendous increases in nutrient inputs through fertilisers (crop production) and concentrated feedstuff (livestock production), higher livestock densities and substantial mechanisation of the sector as such.
The adverse impacts of agriculture on the quality of surface and ground waters were more or less neglected throughout Europe for many decades, but became gradually a priority issue on the political agenda during the 1980s. For example, the EC launched their Nitrates Directive in 1991 (91/676/EC) to control or reduce nitrate losses and eutrophication caused by agricultural activities. Several international conventions were established for the protection of marine and freshwater bodies. They include for example the Oslo-Paris Commission (OSPAR), dealing with the North Sea, and the Helsinki Commission for the protection of the marine environment of the Baltic Sea (HELCOM). The nutrient reduction targets that had been accepted were rather ambitious. The nutrient load to the marine environments for example should be reduced by 50 % within 1995. Eventually it became clear that these targets were difficult, if not impossible to achieve. But maybe the most striking issue was the difficulty to quantify and verify the actual achievements in terms of reduced nutrient loads. This was enhanced by the lack of comparability and transparency in the quantification tools and methods used by the different countries to report on nutrient loads. It became clear that the general understanding of the processes leading to nutrient runoff from agriculture were poorly understood or to put it in other words, the complexity of the processes in the soil-water-biosphere system and its interactions with the socio-economic processes were severely underestimated when the reduction goals were established.
Agriculture represents a major source of nutrient inputs to surface and ground waters throughout Europe as well as in the Baltic Sea Region. Soil loss due to erosion processes on agricultural land and pesticide leaching from intensive crop production are also major issues of concern.
The agricultural pollution sources are usually divided in two groups;
The diffuse sources are of main concern with regard to impacts and control. They are, contrary to most point sources, usually very difficult to quantify accurately while the possible control mechanisms and management options are not necessarily straightforward. This is due to their `diffuse' character with a spatial as well as temporal variability in terms of loads and cause-effect relationships.
This paper outlines in brief some aspects related to the loss processes of nitrogen (N) and phosphorus (P), the potentials for controlling or reducing these losses, and the overall management including monitoring of diffuse agricultural pollution sources.
| | | 3.1 Introduction |