Tasmania Regional Summary
The region
The Tasmanian agroecological zone is centred around Campbell Town and extends from Cressy in the north-west to Mount Morrison in the south-east. Rainfall in the zone ranges from > 1000 mm annum-1 in the north-east to < 600 mm annum-1 in the south-west. Rainfall seasonality ranges is neutral. 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 and barley for the region were produced. A wheat crop with a 5.1 t ha-1 yield and 57 kg of fertiliser N applied ha -1 and a barley crop with a yield of 2.6 t ha-1 with 23 kg 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 crops
- It was assumed that wheat and barley crops had two fallow herbicide applications, one in-crop herbicide application and two in-crop fungicide applications
- Stubble was retained
- Lime was applied at the equivalent rate of 4 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 or barley 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 1.2 and 2.3 t soil loss t product-1. Analysis indicated that Global warming impacts associated with the production of these crops ranged from between 230 and 277 kg CO2-e, Eutrophication impacts ranged between 0.3 and 4.2 kg PO4-e and Particulate Matter impacts ranged between 0.26 and 0.3 kg of < 2.3 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 in the Tasmanian agroecological zone.
Hydrogen ions | Soil erosion | Global warming | Eutrophication | Particulate matter | |
|---|---|---|---|---|---|
(kg H+) | (t soil loss) | (kg CO2-e) | (kg PO4-e) | (kg PM2.3) | |
Wheat | -67.77 | 1.16 | 276.67 | 4.17 | 0.30 |
Barley | -137 | 2.31 | 230.15 | 0.33 | 0.26 |
Greenhouse gas emissions
The emissions profile for both crops modelled for the region shown below in figure 2. For wheat, the greatest source of emissions was the use of fertiliser but fertiliser production also made a considerable contribution to total emissions. The emissions profile of barley production was dominated by fertiliser production and lime use also made a considerable contribution to total emissions.
Figure 2: Greenhouse gas emissions profile for the production of wheat and barley in the Tasmanian agroecological zone.Greenhouse gas mitigation strategies
Mitigation strategies tested for the region were;
- 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;
- 22% by additional lime applications
- 17% 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 198%.
Figure 3: Reductions in greenhouse gas emissions for wheat production when grown with variable fertiliser, additional lime applications and legume - wheat mitigation strategies in the Tasmanian agroecological zone.
Accessible content
Visit accessible versions of the raw data used to generate these charts.
More information
Dr Aaron Simmons
Orange Agricultural Institute
1447 Forest Road
Orange NSW 2800
P: 02 63913894
E: aaron.simmons@dpi.nsw.gov.au
