RECOGNISING THE POTENTIAL OF THE CONTRIBUTION OF GROUNDWATER NITRATES IN THE NUTRIENT BUDGET IN THE BURDEKIN SUGAR INDUSTRY

This project followed on from BBIFMAC's Ground Water Pixel Project, which was aimed at improving water quality to the Great Barrier Reef and surrounding freshwater ecosystems by building the capacity of the Burdekin ground water irrigators to understand and appreciate how the nitrate-N contained in their irrigation water could be utilised in their nutrient budget.

The project encouraged the collaborating farmers to conduct small area strip trials on their farms. They were supported to develop a modified nutrient management strategy that took into account the nitrogen applied through their irrigation water. Nitrate concentrations in groundwater were monitored as well as crop agronomy and final yields.

As growers develop their knowledge and confidence that high crop productivity was still achievable, they were encouraged to expand the area under the improved nutrient management program. This information was extended to other farmers with significant nitrate in their irrigation water.

By gaining a better understanding of the amount of nitrate in our irrigation water and the seasonal variations in concentrations, we are better placed to make decisions about how we can use this nitrate when developing a nutrient management strategy. In the lighter textured soils of the Budrekin Delta, the major mechanism of nutrient loss is deep drainage. The deep drainage of nitrates is causing elevated levels in the aquifer, and this is particularly so where soluble ferrous compounds and associated microbes are absent. While the ultimate fate of the nutrients leached into the water table is largely unknown, it is likely that at least some will be transported to the adjacent marine environment and the Great Barrier Reef lagoon.

For more information on this project, please contact the BBIFMAC office.