A two-day Discussion Meeting of the Royal Society, ‘The Nitrogen
Cycle’, held in London in June
1991 (Stewart & Rosswall, 1992) reviewed the considerable progress
made in understanding the N cycle
in agricultural, forest and aquatic systems. The meeting included
some discussion of the concerns which
were already being expressed at that time over nitrate in water
supplies, and the impacts of nitrogenous
gases on tropospheric chemistry, the greenhouse effect and the
ozone layer. Since then, disquiet over the
impacts of nitrogenous compounds on the environment has increased, and
numerous papers have been
published on many aspects of the problem. We now have much
better understanding of the size and
scale of the perturbation of the N cycle, and several review papers
have highlighted the complexity of
the formidable issues that are challenging environmental scientists
(Vitousek, 1994; Galloway et al., 1995; Vitousek et al.,
1997).