Fraser G et al. (2017), Fertiliser management effects on dissolved inor...

ECB-ART-45649

Environ Monit Assess 2017 Aug 01;1898:409. doi: 10.1007/s10661-017-6115-z.

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Fertiliser management effects on dissolved inorganic nitrogen in runoff from Australian sugarcane farms.

Fraser G , Rohde K , Silburn M .

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Dissolved inorganic nitrogen (DIN) movement from Australian sugarcane farms is believed to be a major cause of crown-of-thorns starfish outbreaks which have reduced the Great Barrier Reef coral cover by ~21% (1985-2012). We develop a daily model of DIN concentration in runoff based on >200 field monitored runoff events. Runoff DIN concentrations were related to nitrogen fertiliser application rates and decreased after application with time and cumulative rainfall. Runoff after liquid fertiliser applications had higher initial DIN concentrations, though these concentrations diminished more rapidly in comparison to granular fertiliser applications. The model was validated using an independent field dataset and provided reasonable estimates of runoff DIN concentrations based on a number of modelling efficiency score results. The runoff DIN concentration model was combined with a water balance cropping model to investigate temporal aspects of sugarcane fertiliser management. Nitrogen fertiliser application in December (start of wet season) had the highest risk of DIN movement, and this was further exacerbated in years with a climate forecast for ''wet'' seasonal conditions. The potential utility of a climate forecasting system to predict forthcoming wet months and hence DIN loss risk is demonstrated. Earlier fertiliser application or reducing fertiliser application rates in seasons with a wet climate forecast may markedly reduce runoff DIN loads; however, it is recommended that these findings be tested at a broader scale.

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Genes referenced: LOC583082

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References [+] :

Bartley, A review of sediment and nutrient concentration data from Australia for use in catchment water quality models. 2012, Pubmed

	Fig. 1. Australian sugarcane-growing regions that drain into the Great Barrier Reef. Locations of experimental sites are shown
	Fig. 2. Accumulated November–June rainfall from Pleystowe station near Victoria Plains and the October SPOTA-1 forecast Queensland Rainfall Index anomaly
	Fig. 3. DIN concentration measured in runoff water relative to a rainfall since application; b days after application; c runoff suspended sediment concentrations; and d total nitrogen input
	Fig. 4. DIN concentrations for a number of runoff events in the time period between 50 and 100 days after fertiliser application. Intermittent increases in runoff DIN concentrations were associated with small runoff events (a) that also had an extended time between the peak rainfall rate and the peak runoff rate (b)
	Fig. 5. Cumulative measured and predicted (using the granular parameterisation) runoff DIN loads (kg N/ha) for the validation site N farm and N replacement treatments. Rainfall, measured and observed DIN load data have been accumulated concurrently from the date of fertiliser application which was set as day 0 for each of the three seasons
	Fig. 6. Predicted average annual DIN load and standard errors for a liquid and b granular nitrogen fertilisers applied at three rates—85, 170 and 255 kg N/ha at four different application times. Standard error bars are shown
	Fig. 7. Accumulated solar radiation and average mill yield for the four major cane growing regions of Queensland
	Fig. 8. Runoff DIN load in the SPOTA-1 forecast ‘wet’, ‘average’ and ‘dry’ years when the nitrogen application rate was 170 or 85 kg/ha for a liquid fertiliser and b granular fertiliser