Water quality associated with nitrate (NO3- leaching from agricultural soil
s is an important environmental issue. This paper describes a new modelling
approach to quantitatively evaluate the effect of the use of fertilisers o
n global nitrate leaching. A global process-based simulation model was prev
iously developed for the nitrogen cycle in terrestrial ecosystems, in which
soil inorganic nitrogen in the form df ammonium (NH4+) and NOS was conside
red. After introducing data on world fertiliser consumption (FAO, 1995) int
o the steady-state model, the extent of disturbance to the nitrogen cycle c
aused by fertilisation was calculated, Although fertilisation resulted in a
n annual increase in net primary production (NPP, represented as carbon) of
18 Gt year(-1). NO3- leaching and gaseous losses of nitrogen oxides and am
monia were also accelerated. Most regions with heavy fertiliser application
lover 100 kg ha(-1) year(-1) . About 2.5% of the land area showed a high a
nnual leaching load equal to or more than 20 kg ha(-1) year occupied by ter
restrial ecosystems suffered a serious leaching load of more than 30 kg ha(
-1) year(-1). Of the total amount of applied fertilisers (138 Tg year(-1))
19% was lost to NO3- leaching, 8% to gaseous ammonia, and 3% to gaseous nit
rogen oxides. The rest was assumed to be fixed in the ecosystems through ve
getation uptake. (C) 2001 Elsevier Science Ltd. All rights reserved.