Phase farming strategies for grains producers in south-east Australia

The potential to use deep-rooted perennials, such as lucerne, for excess groundwater management is limited in annual cropping enterprises in the grain growing regions of southeastern Australia. A scoping study, using a simplified model of plant water use linked to winter water balance was conducted to determine the need for hydrologic intervention in the southern Grains Region, and to identify potential phase farming strategies that were consistent with the need for intervention. The model comprised a water balance equation applied to winter rainfall, linked to spring/summer water use described solely in terms of the residual soil water remaining after the completion of growth in spring and summer. The model was applied to data from Walpeup Vic and Wagga Wagga NSW. The results suggest that crops alone are sufficient for hydrological control in about 70% of the southern Grains Region. Lucerne ameliorated crop leakage in intermediate rainfall zones (about 18% of the region). Both crops and lucerneleaked in high rainfall areas (about 12% of the region). An examination of different phase farming strategies using lucerne, including 'change when wet' and 'change at fixed frequency' strategies, indicated that both strategies could achieve improved water management. However, the preferred strategy was highly dependent on site specific factors, suggesting the need for close monitoring of soil water content and hydrological processes. The results also indicated that successful water management in high rainfall areas required an on-going lucerne presences, thus precluding both annual cropping and the use of phase farming approaches