Nitrogen fertilizer applied in excess of crop needs can cause leaching
of nitrate nitrogen (NO3-N) in the soil profile (Malhi et al., 2002). Nitrate
nitrogen leaching is one of the major pathways for nitrogen losses, especially
in calcareous soil with high pH in which ammonium is easily transformed
to nitrate (Yanan et al., 1997). Leaching is the translocation of soluble salts,
which occurs as water flows down the soil profile. Recent studies have shown
that mineral fertilizer application from agricultural practices is directly responsible
for more than 50% of the nitrogen leached into running waters
(Hansen et al., 2000). The need to collect information relating to application
of different nutrients and their possible effects on environment has
recently become more important due to the pressure on agricultural lands
to feed an ever increasing population of Pakistan. Application of organic
and inorganic fertilizers should be monitored not only for crop production
but also for negative side effects such as leaching into the ground water,
eutrophication, salinity build-up, and other undesirable environmental impacts
(Jolankai, 2004). Leaching of nitrate within the soil profile is normally
dependent on the soil texture, with lighter textured soils more prone to
leaching that the heavier textured soils. Nitrate leaching losses in a loamy
sand soil could be twice as high compared to a clay loam soil.