Reducing Loads through Management Interventions: Results from Douglas Shire Water Quality Monitoring Flume Experiments

Level 1 General Description


This study documented the effect of altering the amount of fertiliser applied to a sugarcane plot, and consequently the quality of water running off the plot as surface water and through the soil profile.

Methods (Brief)

The study was undertaken on a privately owned sugarcane farm in the Saltwater Creek Catchment, approximately 8 km north of Mossman. A paired 9 inch flume trial was set up on this farm. Flume 1 was located in a plot that applied 98 kg N/ha, while flume 2 monitored runoff from a plot that was applied with 190 kg N/ha. Both plots had a slope of equal or less than 0.065%.

In addition to the flume trial, 10 barrel lysimeters were installed to measure the water draining through the soil profile from a defined surface area at a depth of 1m.

Key Findings (Brief)

For flume 1, there were 20 samples analysed with a median TSS concentration of 37.32 mg/L. Flume 2 had 33 samples analysed producing a median TSS concentration of 71 mg/lL Apart from the first sampling, mean, NOx concentrations were always higher in the high N treatment (Flume 2) than in the low N treatment (flume 1). Individual NOx concentrations were as high as 7.5 mg N/L for the low N plot and 15.8 mg N/L for the high N plot.

The main difference between the two flumes is that the sub-surface pathway dominates the TN losses for the high fertiliser site (Flume 1, 58%), and surface water dominates the lower fertiliser application site (Flume 2, 61%). Overall there is approximately 44% more nitrogen being lost to water from Flume 2 than Flume 1.

This study only recorded a low number of samples for the two flumes over the study period; as such, the conclusions drawn from the study are not robust and statistically defensible.


The study is located on Sandy McDonald’s farm, which is approximately 8 km north of Mossman, adjacent to the Saltwater Creek Bridge.

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