Sorghum is the mainstay of Central Queensland dryland farming systems. Its dominance is due to being suited to a summer rainfall pattern and the fact that it could be grown largely without nitrogen fertiliser.
However, low returns, falling levels of soil nitrate and erratic summer rainfall for the majority of recent decades have led many farmers to consider alternatives.
Recent economic modelling confirms that considerable improvement in median yield and gross margin for sorghum is available with a more precise management system.
The graph shows modelled gross margins for wheat and sorghum that could be achieved over the past 100 years of climate history for Capella using current costs and returns. It shows that sorghum gross margin will potentially out-perform wheat gross margin in about 85 per cent of years when both crops are grown using optimal precision and fertiliser inputs.
In 50 per cent of years, wheat at Capella is expected to achieve a gross margin per hectare of about $70 or less. Providing sorghum with improved management and inputs can double this return.
Unfortunately, the farming technologies currently used for sorghum production do not always allow this considerable advantage over wheat to be shown in the paddock.
Remedies cost money
The shortcomings of sorghum in the paddock are mainly due to establishment problems (which can cause an average 30 per cent yield loss), lodging difficulties, soil nitrogen run-down and harvest losses.
A potential net benefit of at least $25,000,000 in Central Queensland could be gained by reducing the effect of these problems. (This is the current value of the expected benefits that will accrue to the industry from implementing the changes.)
But, achieving this potential benefit does not come without incurring substantial costs. Assessment of the costs of improving the precision of the sorghum farming system shows that while they are not insurmountable, many farm businesses are unlikely to be able to immediately finance the necessary equipment and/or unwilling to incur the additional risk of applying increasing amounts of nitrogen fertiliser.
To add N or a pasture phase?
The options now available to local farmers considering how to turn a profit are complex. The choice is between a non-sustainable farming system that relied upon nitrogen extraction for its profitability (no longer an option now that most of the N has been extracted) and a variety of sustainable options, which carry higher input costs and therefore higher risks. Sustainability is the core investment issue.
Farm managers could invest in a much more precise sorghum farming system that is more expensive, more risky, but potentially of similar profitability as the low-input unsustainable farming systems.
(The authors note that growing sorghum without N on low-N soils is a recipe for disaster.)
They could also invest in a ley farming system that requires lower or nil nitrogen fertiliser inputs, may reduce overall farming costs, could spread risk by increasing income diversification, but may reduce profitability.
Another choice is to return the paddock to permanent pasture once the cropping phase has reduced soil nitrates to low levels. This is a lower-risk, lower-profit option again.
To make the choice in a reasoned way requires much information about the capacity of the soil resource, the nature of the individual farm businesses involved and the preferences of the farm managers.
On-farm trials are currently addressing more precise farming systems as well as ley farming options.
If the choice is ley farming, sorghum will still need to be grown with precision and management to achieve its full potential. However, in this situation the contribution of sorghum growing to farm business risk will be reduced due to a lower reliance on fertiliser inputs and a smaller proportion of the farm being planted to the crop at any one time.
Program 3.5.1 Contact: Mr Fred Chudleigh 07 4983 7400
Optimal gross margins for sorghum and wheat on a soil that stores a maximum of 120 mm available water and has medium soil nitrogen at Capella as modelled by APSIM.