Vic High Rainfall Regional Summary

The region

The Vic High Rainfall agroecological zone occurs in two portions. The eastern portion is centred around Stanhope while the western portion starts near Dartmoor in the west and curves around through Ararat with the north-eastern extent of the zone being Castlemaine. Rainfall in the zone ranges from > 800 mm annum^-1 in the south-west to < 600 mm annum^-1 in north-east of the zone. Rainfall seasonality is winter-dominant. Boundaries for the zone are shown in Figure 1.

Modelling regional practices

Producing models that reflect all farming practices throughout a region is difficult so “common practice” models for wheat, barley and faba beans for the region were produced. A wheat crop with a 3.0 t ha^-1 yield and 53 kg of fertiliser N applied ha ^-1, a barley crop with a yield of 1.7 t ha^-1 with 56 kg fertiliser N ha ^-1 applied and a faba beans crop with a yield of 0.9 t ha^-1 and 7 kg of fertiliser N ha ^-1 applied were modelled. The key assumptions of these models were that;

• Only one pass was made at sowing
• Split fertiliser applications were used for wheat and canola crops
• It was assumed that all crops had two fallow herbicide sprays and canola also had a pre-emergent herbicide application. Wheat and canola had one in-crop herbicide application each and faba beans had two. Wheat crops assumed to have one fungicide application while canola and faba beans had two.
• Stubble was retained
• Lime was applied at the equivalent rate of 5 t ha^-1 every decade and incorporated through scarification

Impact indicators

Hydrogen ion impacts estimate the release of hydrogen ions to the soil associated with crop production. A negative value indicates a reduction in soil acidity whereas a positive value indicates an increase in soil acidity. Soil erosion is an estimate of soil loss that occurs during the production of the crop. The depth of soil lost will depend on many things but an approximate conversion is that 1.5 t of soil loss equals 1 mm of soil. Global warming impacts are the release of greenhouse gases to the atmosphere expressed as carbon dioxide equivalents (CO₂-e), Eutrophication impacts are the release of phosphorous to the environment and are expressed as phosphate equivalents and Particulate Matter impacts are the release of fine particles less than 2.3 micrometres in diameter.

Benchmark results

Results below in Table 1 show the environmental impacts of producing a t of wheat, barley or faba beans in the region. Lime use in the region resulted in a reduction in free hydrogen ions in the soil for all crops and soil erosion was estimated at between 2.6 and 6.6 t soil loss t product^-1. Analysis indicates that Global warming impacts associated with the production of these crops ranged from between 192 and 606 kg CO₂-e, Eutrophication impacts ranged between 2.2 and 4.8 kg PO₄-e and Particulate Matter impacts ranged between 0.25 and 0.6 kg of < 2.5 µm particulate matter t product^-1.

Table 1: Hydrogen ion changes, soil erosion and Global Warming, Eutrophication and Particulate matter impacts associated with the production of wheat, barley and faba beans in the Vic High Rainfall agroecological zone.

Greenhouse gas emissions

The emissions profile for all three crops are shown below in figure 2. The emissions profile of wheat and barley were dominated by fertiliser production and use and residue emissions were also relatively high. Emissions from the production of faba beans were dominated by fertiliser production and use, and emissions associated with residue breakdown and chemical production.

Greenhouse gas mitigation strategies

Mitigation strategies tested for the region were;

• Sustainable intensification
• Additional applications of lime
• Implementation of variable rate fertiliser technology
• Changing a wheat-wheat rotation to a legume-wheat rotation

More information on the assumptions used to test these strategies and how they might reflect individual enterprises are available on the Mitigation strategies page.

Results (figure 3 below) indicate that emissions of a t of wheat can be reduced by;

• 71% through the implementation of sustainable intensification
• 8% by additional lime applications
• 18% by implementation of variable rate fertiliser technology

Results also indicate the replacing a wheat crop with a legume crop in a two-crop rotation can increase greenhouse gas emissions intensity by 171%.

More information

Dr Aaron Simmons
Orange Agricultural Institute
1447 Forest Road
Orange NSW 2800
P: 02 63913894
E: aaron.simmons@dpi.nsw.gov.au