There are small differences in the way irrigation, and dairy factory effluents are modelled. First, the N in irrigation is treated as inorganic N whereas a portion dairy factory effluent contains inorganic and organic N. These differences can affect background N leaching, and pasture N concentrations, hence N intake, excreta deposition, and urine N leaching. There is a small difference in the way water is added resulting in slightly different drainage.
Which ever method is chosen to enter Dairy Factory Effluent, consistency is important. Over time the method used for the farm description should stay the same and changing input approach will provide false differences in the results.