Maize productivity in southern New South Wales under furrow and pressurised irrigation

Irrigation farmers in the Murray-Darling Basin of Australia are under considerable pressure to reduce the amount of water they use for irrigation, while sustaining production and profitability. Changing from surface to pressurised irrigation systems may provide some or all of these outcomes; however, little is known about the performance of alternative irrigation methods for broadacre annual crops in this region. Therefore, a demonstration site for comparing furrow, subsurface drip and sprinkler irrigation was established on a representative clay soil in the Coleambally Irrigation Area, NSW. The performance of maize (Zea mays L.) under the three irrigation systems was compared during the 2004-05 season. Subsurface drip irrigated maize out-performed sprinkler and furrow irrigated maize in terms of grain yield (drip 11.8 t/ha, sprinkler 10.5 t/ha, furrow 10.1 t/ha at 14% moisture), net irrigation water application (drip 5.1 ML/ha, sprinkler 6.2 ML/ha, furrow 5.3 ML/ha), net irrigation water productivity (drip 2.3 t/ML, sprinkler 1.7 t/ML, furrow 1.9 t/ML) and total water productivity (drip 1.7 t/ML, sprinkler 1.4 t/ML, furrow 1.3 t/ML). Thus, subsurface drip irrigation saved similar to 30% of the total amount of water (irrigation, rain, soil water) needed to produce the same quantity of grain using furrow irrigation, while sprinkler irrigation saved similar to 8% of the water used. The higher net irrigation with sprinkler irrigation was largely due to the lower soil water content in the sprinkler block at the time of sowing. An EM31 survey indicated considerable spatial soil variability within each irrigation block, and all irrigation systems had spatially variable water distribution. Yield variability was very high within all irrigation systems, and appeared to be more strongly associated with irrigation variability than soil variability. All irrigation blocks had large patches of early senescence and poor cob fill, which appeared to be due to nitrogen and/or water deficit stress. We expect that crop performance under all irrigation systems can be improved by improving irrigation, soil and N management.