Business implications of a changing climate

Author: | Date: 05 Sep 2016

Take home messages

• Summer rainfall has been steadily increasing, but since 2000 winter rain has dropped.
• Wheat yield variability has increased with wheat seeding and spring rainfall decreasing.
• Early and late summer rain has increased providing more soil moisture for winter crops, but also more opportunities for summer crops in rotations.
• The rate of yield increase in sorghum yields was much higher than that for wheat yields.

Background

To assist the GRDC in defining new sub-regions and understanding what climate changes were occurring, an analysis was made by the Australian Export Grains Innovation Centre (AEGIC) of rainfall changes since 2000. This complimented spatial maps of wheat and sorghum yield trends carried out in a previous GRDC project (Stephens et al., 2011) which was updated with recent data.

Methodology

Changes in mean fortnightly rainfall were graphed for key rainfall stations while yield trends, yield variability and water use efficiencies were determined with crop water balance models.

Results and discussion

Since 2000 results show that each fortnight has been drier at Dubbo in the winter growing season between May-October, except for the first fortnight in June (Figure 1). The largest decrease in rainfall was found in the wheat seeding time and in August through early spring. Conversely, the early and late summer rainfall increased considerably, though January was drier (Figure 1). The wetter summers appear to go hand in hand with higher sorghum yield trends, while lower winter rainfall has coincided with lower wheat yield trends  (Table 1, Stephens et al., 2011).

Line graph showing average fortnightly rainfall for Dubbo in the last 90 years of the 20th century compared to the first 15 years of the 21st century.

Figure 1: Average fortnightly rainfall for Dubbo in the last 90 years of the 20th century compared to the first 15 years of the 21st century. 

Table 1: Changes in climate and yields for north-western statistical division, NSW.

Crop  Rainfall change (period) Yield change since 1990
Wheat -5% to -20% (May-October) 0%-1% per annum
Sorghum  0% to 20% increase (Nov-Apr) 2%-5% per annum

Another change since 2000 has been the increased yield variability of wheat, particularly in southern New South Wales (NSW). Mean temperatures in spring have warmed the most compared to any other season and this has put stress on crops in both the flowering and grainfilling stages. Water use efficiencies (WUE) are only 40-60 per cent of their potential, so ways of increasing WUE in a more water limiting environment should be sought. Early sowing appears to offer a way to address WUE and high heat concerns, though frosts still remain a concern. In a more variable climate growers tend to be more conservative with fertilisers, however this works against higher WUE in wetter years. Recently, the NSW government announced a rebate for multi-peril crop insurance. Having income protection in years when more outlays are made could underpin higher WUE and could contribute to more profitability in the long run? 

Conclusion

A southward shift in rainfall zones and rising mean temperatures means that the climate experienced now in central NSW is more like that experienced previously by regions further north; i.e. more summer rain, less winter rain. Increased summer rain, combined with larger technological advances in yields of crops like sorghum means that the mix of summer crops in rotations needs to be reconsidered. Ways of increasing WUE in wheat without increasing financial risk should also be pursued in a more water limiting environment.

Useful resources

http://www.agromet.com.au, 

GRDC Ground Cover May-June 2016, New Climate Zones. 

Stephens, D.J., Potgieter, A.P., Walcott, J. And Nunweek, M. (2011) GRDC strategic planning for investment based on agro-ecological zones – second phase. 

Final Report to GRDC, Department of Agriculture and Food, Western Australia, Perth, 156p. 

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through their support of the GRDC, the author would like to thank them for their continued support. 

Contact details 

David Stephens
3 Baron Hay Court, South Perth, WA 6108
0403001318
david.stephens@agromet.com.au