Water-soluble nitrates and phosphates have been considered to
be the two potential pollutants emitted to the water compartments
during rice cropping. A similar approach was carried out for both of
these pollutants. Paddy rice consumes significantly more ammonia
than nitrates, in contrast to other global crops. Because urea and
ammonium-based fertilisers prevail in Northeastern Thailand,
direct nitrate emissions result mostly from biochemical transformations
(e.g., nitrification) and the whole nitrogen cycle and
balance rather than from direct fertiliser loss. The principles underlying
the nitrate emission assessment are that (1) nitrates form
the remaining components of the overall nitrogen mass balance,
the other components of which were determined in earlier sections;
(2) these water-soluble nitrates may leach to the water
compartment through surface drainage and deep percolation; and
(3) such a portion refers to the ratio betweenwater that is not used
by the crop and overall water supply; in other words, it relates to
water use efficiency.