Effects of agricultural land use changes on diffuse pollution of water resources

Lysimeter trials carried out over several years showed that cutting mineral fertilizer by 50% does not immediately result in a reduction of the leaching losses of relevant macronutrients (N, P, K). Land usage changes in the form of 1‐year rotating set‐asides entail greater N‐leaching compared to best management practices (BMP). By contrast, after set‐aside lasting 3–5 years, reductions in N‐leaching of 25–45% must be expected. Lysimeter trials of reintegrating land set‐aside for a number of years into intensive agriculture without increasing N‐leaching losses are presented. Ways of scaling up lysimeter results to fields and small catchments are described, as well as areas where research still needs to be carried out are discussed. Copyright © 2002 John Wiley & Sons, Ltd.