Abstract:
More than half of the world's population consumes rice as the staple food and Australia
produces 1.2 million tons of rice per year feeding around 40 million people daily. Future climate
change predicts increase temperatures and reduction in water availability due to reduced
rainfall. Rice production heavily relies on climatic changes especially atmospheric temperature
and rain fall. This study evaluated the responses of different rice varieties to change in
temperature (associated with elevated atmospheric CO2 concentration) and rainfall using
APSIM–Oryza model at two sites, Griffith/ Riverina in New South Wales and Kununurra in
Western Australia. Varieties used at Riverina were Amaroo, Langi, and Quest, representing late,
mid and early maturity types, respectively. Variety (IR72) was used for Kununurra region. Five
different changes of temperature were 0 (base temperature 300C), +1, +2, +3, +4oC with a
combination of five rainfall changes (+10, 0, -10, -20, and -30%) used in the simulation to
represent the series of projected climatic changes predicted for Australia over the next 60 years.
The corresponding CO2 concentrations allied with above temperature levels were 380, 435, 535,
640 and 750 ppm. All three rice varieties in two Riverina climatic zones showed a yield increase
of 0.36 tons/ha (up to 10%) with increase in temperature by 2o C at Griffith, which could be due
to CO2 fertilization effect. Further increase in temperature caused a steady decline in yield, with
short season variety ‘Quest’ affected least. Grain yields at Kununurra steadily declined by 37%
with 4oC increase in temperature. These results indicated that warmer temperatures would
increase spikelet sterility. Adaptations could be included, use of shorter season varieties and
changing planting dates. In the above two different climatic zones, higher temperature is
expected to limit rice production in future.
