Estimating the effects of set-aside on water quality: Scaling-up of lysimeter studies

Since 1990, agriculture in the five new federal states of Germany has exper ienced a fundamental structural change. As much as 10 per cent of the 6.2 m illion ha of previously intensively farmed agricultural land were set-aside abruptly. In the spring of 1991, a lysimeter trial (filled with soils comm on in the catchment area of the Elbe River), was set up to investigate the impact of set-aside on the water and solute balance. The studies proved tha t restricting agricultural use in areas previously farmed intensively by co nverting them into permanent, or rotation fallow will result in measurable changes in deep percolation (ground-water recharge) and water quality in le ss than one year. The results of the lysimeter studies were extrapolated to calculate the effects of set-aside in a catchment area (about 2500 ha) wit h similar meteorological and soil conditions. The calculations showed that increasing the area under rotation fallow from 8 to 15 per cent increases t he nitrogen load of the stream draining the catchment by about 5 per cent. Copyright (C) 1999 John Wiley & Sons, Ltd.