Climatic and agronomic conditions
Australian Crop Report: September edition
Following above average rainfall from January to April, May to July rainfall was extremely low to below average in most cropping regions in Victoria, Queensland, South Australia and Western Australia. In cropping regions in New South Wales, May to July rainfall ranged from well below average to above average (Map 1).
Despite variable rainfall in June and July, close to average yield potentials were preserved across most cropping regions due to a draw down of soil moisture reserves built up during late summer and autumn.
August rainfall was generally average to above average in most cropping regions except for some southern cropping regions in Western Australia and South Australia where August rainfall was below average (Map 2). Substantial August rainfall improved soil moisture across most cropping regions, supporting the final stages of winter crop development and providing a reliable base for the early planting of summer crops.
Map 3 shows the relative levels of modelled root zone (0 to ~1 metres) soil moisture for cropping zones across Australia for August 2020. Soil moisture estimates are relative to the historical long-term average (1911 to 2016) and presented in percentiles.
Relative root zone soil moisture for August 2020 was around average to above average for this time of year in most cropping regions in the eastern states. In contrast root zone soil moisture was average to extremely low for this time of year in South Australian and Western Australian cropping regions (Map 3).
The rainfall outlook presented here provides an indication of how favourable conditions for agricultural production are likely to be over spring. The latest three-month rainfall outlook (September to November), issued by the Bureau of Meteorology on 3 September 2020, suggests that spring rainfall is likely to be above average in most cropping regions. However, there are roughly equal chances of higher or lower than average spring rainfall in most cropping regions in Western Australia and below average spring rainfall is most likely in the Geraldton zone in Western Australia and part of the Kwinana zone. (Map 4). It is likely rainfall will not be evenly distributed in most cropping regions over spring with a lower chance of exceeding average rainfall in September than in October and November.
There is a 75% chance of between 25 and 100 millimetres in most cropping regions in Australia during September and October (Map 5). It is highly likely spring rainfall totals will be enough to maintain average to above average crop yields through to harvest in regions where crops were in a good position at the end of winter.
There is a 75% chance of rainfall between 10 and 50 millimetres in most cropping regions in Western Australia and northern cropping regions in Queensland. In areas with low levels of soil moisture at the start of spring these probable September to October rainfall totals are unlikely to be sufficient to sustain the current winter crop yield potentials through to harvest.
The outlook for maximum and minimum temperatures for September to November 2020 indicates that daytime temperatures are likely to be around average in spring in most cropping regions. Night-time temperatures are expected to be hotter than average in most cropping regions except in Western Australia where they are more likely to be around average.
At the end of August 2020, there was a 75% chance of achieving at least 265 millimetres of water availability by the end of October 2020 in eastern and central cropping regions in New South Wales, southern cropping regions in Victoria, central and southern cropping regions in South Australia and far western and southern cropping regions in Western Australia. There is a 75% chance of achieving between 140 and 235 millimetres of water availability by the end of October 2020 in north-western and south-western cropping regions in New South Wales, most cropping regions in Queensland, northern cropping regions in Victoria and South Australia, and most cropping regions in Western Australia.