By Andries Potgieter
Advance knowledge of the likely size of a summer crop is highly sought-after by government bodies and agri-industry players such as grain handlers. To get a better handle on this, researchers at the Queensland Department of Primary Industries and Fisheries have developed a regional commodity forecasting system. This integrates:
These projected data are drawn from historical analogue years based on similarity to the prevailing phase of the Southern Oscillation Index.
The sorghum model is run from 1 April the year before harvest to account for the influence of the winter fallow and starting soil moisture conditions.
The model has been calibrated against actual shire sorghum yields from the Australian Bureau of Statistics for the period 1983 to 1997. Cross-validated correlations ranged from 0.6 to 0.9 within the main sorghum-producing shires of north-east Australia.
Using this model, the current sorghum outlook for north-east Australia as a whole is close to the long-term expectation with the forecast median yield at the end of February this year of 2.15 tonnes per hectare. This is just below the long-term median of 2.20t/ha and falls into the 39th percentile relative to all years (1901-2003).
There remains, however, much variation in the outlook among local regions (Figure 1).
Most areas in central Queensland show slightly below average crop yield expectations falling in the 49th percentile of all years. Areas in southern Queensland show very much below-average crop-yield expectations falling in the 21st percentile of all years, while conversely most areas in northern NSW show predicted yield outcomes much above normal, falling in the 76th percentile rank relative to all years.
With maturity being reached for almost all of the planted crops in the north-east cropping region, projected rainfall for the remainder of the growing seaon will have little to no effect on the final realised yield. However, a wet finish will increase the chance of diseases or pests and could reduce yield outcomes.
The outputs from this system are used by government agencies to assist them in their commodity outlooks, and other government bodies to help in exceptional circumstances decision-making.
Bulk handlers use this information to forward buy or sell and shift resources from one area to another, depending on the predicted sorghum crop figure in a specific region.
For more information: Andries Potgieter, 07 4688 1417, Andries.Potgieter@dpi.qld.gov.au; or visit www.dpi.qld.gov.au/fieldcrops and follow the link to Seasonal Crop Outlook - Sorghum, February 2005.