In the cropping systems under study, the pesticides typically
used include a molluscicide (solid pellets, metaldehyde-based), an
insecticide (liquid, isoprocarb-based with CaCO3 as humectant
additive) and an herbicide (liquid, glyphosate-based); all are handsprayed
at different stages while the field is flooded most of the
time. It was assumed that 100% of pesticides ultimately end up in
both soil and water compartments because none of the pesticide is
supposed to concentrate in the rice grain and leave the field at
harvest. Straw and rooting systems are left in the field to decay.
Under these circumstances, it was arbitrarily decided to split
emissions equally between soil and water compartments (50%e
50%).