The Mackay Irrigation Project, a win for growers and the Reef

Sufficient water promotes a healthy sugarcane crop and increased productivity. In the Mackay Whitsunday region, much of the available irrigation water is not used due to pumping costs or available infrastructure. The Sugar Research Australia Central Region District Plan aims to increase utilisation by 22 percent, underscoring the regions irrigation potential. 

The Mackay Irrigation Project, delivered by CANEGROWERS Mackay, was funded by the partnership between the Australian Government's Reef Trust and the Great Barrier Reef Foundation. 

Twelve sugarcane growers were supported to improve irrigation practices and system efficiencies across more than 3700 hectares of cane land. Participating growers reduced their costs, increased productivity gains against previous 10-year average, and enhanced nutrient use efficiency across all crop classes.  

The irrigation project provided management strategies to increase productivity and profitability. Project irrigation, productivity and soil data was collected, interpreted and shared to increase knowledge and understanding across the Mackay Whitsundays sugarcane industry.  

Over 30 soil cores were collected across various soil types to identify the physical and chemical characteristics to understand how this affects water holding capacity. Soil moisture probes were installed in predominant soil types, gathering data along the soil profile to 1.2m depth. This real-time data provided growers with information on readily available water and refill points, while also measuring Volumetric Ion Content to understand how the crop uptakes applied nutrients and the movement of nutrients down the soil profile. 

The soil core and probe data was used to inform modelling platforms including APSIM (Agricultural Production Systems sIMulator), IrriSat (irrigation decision support system) and IrrigWeb (sugarcane irrigation scheduling tool), visually displaying moisture drawdown for optimal irrigation time recommendations. The soil moisture information, coupled with an irrigation efficiency audit ensured that growers were getting water onto their paddocks as cheaply and as efficiently as possible.

Marian grower, Peter said, “The problem was that I could not get enough water on quickly enough and it was labour intensive impacting my other farm management tasks."  

Peter said infrastructure upgrades and equipment optimisation reduced his pumping costs from an estimated $142 to $110 per megalitre (ML) of water applied, increasing his water usage by 200ML per annum. Real-time data from probes and crop growth modelling, and remote access to pumps via mobile has saved up to 300 labour hours per annum spent on irrigation management.  

Another key component of the Mackay Irrigation Project was optimising block alignments to facilitate rapid post-harvest irrigation. 

“One of the major issues under a centre pivot is attempting to re-establish the ratoon crop as quickly as possible but harvesting operations impact on the ability to do that. By cutting the Pivot into 4 management units we are better able to achieve this. Sometimes you can lose a whole month of growth before cutting an area out,” said Ross another grower involved from Bakers Creek. 

Growers are now planning for future irrigation management units to operate independently of harvest schedules. Irrigation efficiency will significantly increase when blocks can be accessed when the crop requires water. 

The Mackay Irrigation Project was one of eight projects under the Mackay Whitsunday Water Quality Program. This project demonstrated that improving irrigation efficiency and scheduling improves regional productivity in nutrient use efficiency providing a win for both growers and the water quality flowing to the local waterways and the Reef.