The SA Vic Bordertown Wimmera agroecological zone the Coorong, SA in the west to Kyabram in the east. Rainfall in the zone ranges from > 600 mm annum-1 south-west to < 400 mm annum-1 in the north-east and rainfall seasonality is winter dominant. Boundaries for the zone are shown in Figure 1.
Producing models that reflect all farming practices throughout a region is difficult so “common practice” models for wheat, barley and lentils for the region were produced. A wheat crop with a 2.3 t ha-1 yield and 29 kg of fertiliser N applied ha -1, a barley crop with a yield of 2.2 t ha-1 with 29 kg fertiliser N ha -1 applied and a lentils crop with a yield of 1.4 t ha-1 and 5 kg of fertiliser N ha -1 applied were modelled. The key assumptions of these models were that;
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.
Results below in Table 1 show the environmental impacts of producing a t of wheat, barley or lentils in the region. An absence of lime use in the region resulted in an increase in free hydrogen ions in the soil for all crops and soil erosion was estimated at between 4.3 and 7.2 t soil loss t product-1. Analysis indicated that Global warming impacts associated with the production of these crops ranged from between 75 and 261 kg CO2-e, Eutrophication impacts ranged between 1.5 and 2.1 kg PO4-e and Particulate Matter impacts ranged between 0.14 and 0.24 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 lentils in the SA Vic Bordertown Wimmera 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 | 1.71 | 4.33 | 254.14 | 1.93 | 0.23 |
Barley | 1.82 | 4.61 | 260.94 | 2.05 | 0.24 |
Lentils | 1.29 | 7.16 | 74.65 | 1.48 | 0.14 |
The emissions profile of all three crops are shown below in figure 2. For wheat and barley, the greatest source of emissions was the use of fertiliser. The production of fertilisers and residue breakdown also made a relatively high contribution to total emissions where as other emissions sources were relativel low. Emissions from residue dominated the emissions profile of lentil production mainly because lentil production used realtively small amounts of fertiliser.
Figure 2: Greenhouse gas emissions profile for the production of wheat, barley and lentils in the SA Vic Bordertown Wimmera agroecological zone.Mitigation strategies tested for the region were;
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;
Results also indicate the replacing a wheat crop with a legume crop in a two-crop rotation can increase greenhouse gas emissions intensity by 173%.
Figure 3: Reductions in greenhouse gas emissions for wheat production when grown with sustainable intensification, variable fertiliser and legume - wheat mitigation strategies in the SA Vic Bordertown Wimmera agroecological zone.
Visit accessible versions of the raw data used to generate these charts.
Dr Aaron Simmons
Orange Agricultural Institute
1447 Forest Road
Orange NSW 2800
P: 02 63913894
E: aaron.simmons@dpi.nsw.gov.au