Rice growing in Australia is confined to the Riverina region of New South Wales (NSW) centred at 35oS, 146oE. There is very little variation in altitude (120m) across the rice producing areas. Approximately 140,000ha are sown each year, producing industry-wide average yields up to 9.4t/ha, with the highest yielding crops exceeding 13t/ha. Although rice growing areas to the south are 1-2oC cooler than the north, there is generally little temperature variability across the rice growing area. The average rainfall during the growing season is 200mm with the crop requiring full irrigation. The growing season is characterised by long days with high levels of solar radiation. Low temperatures during establishment and a cool grain-filling period restrict the length of the growth season, while low night temperatures during reproductive development can cause catastrophic yield loss.
There is a single crop grown each year, which is planted in spring, grows through the summer and is harvested in autumn. Rice planting starts in late September, as soon as the risk of frost is negligible. Full season cultivars and short season cultivars are sown in early October and November respectively to ensure that reproductive development coincides with greatest chance of warm night temperatures (late January-early February). Grain filling occurs in February-March when the cooler temperatures extend the duration of grain filling producing grains of high quality. Rice crops are drained and harvested in March -April, prior to the first frosts, when the moisture content is between 16-22%.
Over 90% of Australian rice crops are sown aerially. The majority of nitrogen is applied prior to permanent flood and if required top-dressed at panicle initiation. Average N application rates are 80-100 kg N/ha.
The Lao People's Democratic Republic (Lao PDR) is located in the tropics, between the latitudes 14oN and 22oN and longitudes 100oE and 108oE. The rice area in Laos is 650,000ha, producing average yields of 2.7t/ha, with the highest yields reaching 4t/ha. The Lao PDR is divided into the northern, central and southern regions, each having different temperature regimes due to variations in altitude and latitude. Laos has a distinct wet and dry season. Historically, the majority of rice production in Laos has been produced during the wet season as upland and lowland crops. With the advent of irrigation, rice production in the dry season has increased from 13,600ha in 1995 to 87,000ha in 1999 (NAFRI, 2000). The wet season crop is transplanted into the field in June and harvested in October, while the dry season crop is transplanted between November and January and harvested in May. Of the rice produced in Laos in 1998, the rainfed lowlands accounted for 74%, the rainfed uplands 13% and 13% was irrigated (IRRI 1999). The long-term aim for Laos rice production is to reduce the area of rainfed upland rice and increase irrigated rice. Almost all of the rice in Laos is transplanted by hand and harvested by non-mechanised methods. The impact of low temperature on rice production relates specifically to the dry -season crop at both the establishment and reproductive stages. Elevation and latitude principally determine temperature variation between provinces within Laos. Champassak, a southern province (15oN), has an elevation of 120 metres, and high temperatures during flowering in April (Figure 1-F) sometimes limit dry season yields. In comparison, Xieng Khouang has an elevation of 1050 metres and is located at latitude of 19.5oN. It suffers from low temperature at establishment and microspore stages in the dry season (Figure 1-D). The temperature patterns in all six provinces show that the average minimum temperatures slowly decrease from November through to December throughout the early establishment phase (Figure 1).
