Grain sorghum is a summer-growing grass native to Africa and Asia, and is produced in large quantities throughout the USA, China, India and Africa, where it is used for both human and animal consumption. It has also been grown in Queensland and NSW, where it is marketed primarily as a stockfeed.
There are no proven production packages for sorghum in dryland farming systems in WA. Information presented here is largely based on work from the eastern States. It should be treated as an experimental crop until more is known about local performance.
Grain sorghum is one of the most drought-tolerant grain crops, giving some potential for production in lower rainfall areas.
Despite this drought tolerance, it requires adequate moisture at critical periods. Lack of moisture during flowering and grain filling will severely affect the yield potential.
In high moisture situations it yields well (10 to 12 tonnes per hectare). Yield potential in the eastern States is calculated as 15 kg/mm of available moisture after the first 100 to 110 mm.
Insufficient local data exists to calculate potential production here but it is not expected to exceed that observed in the eastern States.
Rotation:
Grain sorghum can be grown in rotation with cereals, legumes, pastures, fallow, oilseeds and cover crops. Check the herbicide history of the paddock and the plant-back periods for residual herbicides used over the past two seasons particularly for sulfonylureas, e.g. Glean (18 months) and Logran (22 months).
At present, it is difficult to get two crops in any one year. Summer crop cannot normally follow winter crop because:
- winter crop harvest is later than the ideal summer crop sowing window
- stored moisture in the soil following a winter crop is likely to be low
- in the cooler south-west (Great Southern and south coastal regions) grain sorghum harvest may conflict with the preparation and sowing of the winter crop and may require driers to reduce moisture content to acceptable levels
It may be possible to increase intensity by growing a summer crop immediately following a winter crop if the winter crop is swathed or cut and harvested early (e.g. Unicorn barley, canola, hay). Some farmers are exploring the option of sowing grain sorghum into a winter crop before harvest if soil moisture status is high but this needs more investigation.
Alternatively, it may be possible for grain sorghum to be ratooned in areas of mild, relatively frost-free winters, allowing it to continue growing after harvest to produce more grain in the following summer.
Paddock selection:
Choose a paddock with a high level of stubble residue (more than 80% ground cover) to prevent soil moisture loss over summer and to protect against wind erosion. Well drained soils with good water-holding capacity are best.
Sorghum prefers a near neutral pH but has been grown on soils with pH 4.8 to 5.5 (CaCl2 ). At these low pH levels production is likely to be reduced (although lime may increase productivity).
Sorghum is moderately salt-tolerant between that of wheat and barley. Germinating and young plants less than six weeks of age are most sensitive to saline conditions.
Sorghum has a fibrous root system and can extract moisture from depth, therefore good yields will be most likely when the soil profile is full of moisture at seeding.
Shallow soils (less than 1 metre deep), waterlogged soils and acid soils with a pH of less than 4.5 should be avoided. The site should have a low weed burden, because in-crop herbicide options are limited.
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