Water and nitrogen (N) are widely considered the two most important nutrients that limit production of pasture and crops. Maize crop requires a high amount of water and N inputs for optimum production because of the large amount of dry matter (DM) produced. Garcia et al. (2008) reported a total of 27 t DM/ha from maize in spring–summer (late October – mid February) using 4 mega liter (ML) of irrigation water compared to 17 t DM/ha from pastures for the whole year using ∼8 ML of irrigation water. In many Australian dairy farms, maize is grown for silage which in turn is used to complement cow's diets at times when pasture quality is low (autumn–winter mainly). However, despite the high potential forage yield, the problem of growing maize for silage in many key dairy regions is that high water and N inputs are needed to maximize forage yield. Current predictions of global climate change impact suggest that irrigation water availability may decline in the future globally (World Water Assessment Program, 2009). This situation of declining water availability may impact on future price and availability of irrigation water.