Characterising the risk of heat stress on wheat in South Australia: meteorology, climatology and the design of a field heating chamber

Abstract

High temperatures during spring have long been recognised as one of the weather risks for grain farmers. Recent events such as 12 October 2004 and 15 November 2009 raise questions about the likelihood of this risk and the consequences on grain crops. This paper reports on work first characterising the likelihood of heat events by considering meteorology (synoptic weather patterns) and climatology (analysis of climate records) and second studying the consequences by reproducing these heat events in the field using a purpose built chamber. Spring heat events in the SA grains belt are due to a northerly flow of air associated with a passing high pressure system to the east of the region and an approaching cold front to the west. Analysing the climatology of heat events in the context of crop phenology typical of a region, it is apparent that a medium rainfall region like Roseworthy (flowering later in October) may be at a greater risk of heat events than a much warmer, low rainfall location like Minnipa (flowering in September). Preliminary results indicate that a relatively inexpensive chamber can be used to impose a single day heat event in the field (maximum temperature of 35°C). The chamber was able to heat by up to 12°C above ambient.