USE OF OVERHEAD IRRIGATION IN THE LOWER BURDEKIN USES LESS WATER AND DOES NOT PENALISE YIELD

FOR several years, the MAFIA Grower Group in the Burdekin region has taken a proactive approach to managing their farming systems. As a consequence, the group has actively engaged with researchers to gain a better understanding of the natural resource management, productivity and economic issues relating to their farming enterprises. In early 2007, Hesp Farming set up two adjacent paddocks; one to be irrigated using furrow irrigation, the second to be irrigated with a lateral move irrigator. Both fields were instrumented to capture irrigation usage, run off and drainage below the root zone. Sugarcane was planted in both blocks in March 2007. The OHLP was used to apply between 6–50 mm water 41 times making a total of 1096 mm (11 ML/ha) while the Furrow block received a total of 2144 mm in 21 applications of 74–171 mm each. Cane and sucrose yields were similar for both blocks with the OHLP block yielding 154 and 23.5 t/ha cane and sucrose and the Furrow block 151 and 24.1 t/ha. Water use efficiency for the OHLP was therefore 8.7 t cane/ML compared to 6.4 for the Furrow block. Soil moisture, runoff and drainage measurements were used to obtain hydraulic parameters for the soil in the Furrow block. These data were used to simulate the water balance and crop stress responses for both Furrow and OHLP blocks using the WaterSense sugarcane model. From this we fully accounted for all terms in the water balance (runoff, drainage, evapotranspiration and soil storage) to illustrate the benefits of the OHLP system in terms of reduced runoff and drainage as well as the risks to yield associated with reduced volume, but more frequent irrigation compared to the Furrow system.