Weed competition during the establishment phase of sorghum can result in poor establishment, uneven maturity and harvest delays. Where weeds compete with the crop for nutrients and moisture, a yield penalty often occurs.

Key points

• Weeds need to be managed well to achieve high yields.
• A lack of post-emergent herbicide options for grass control in sorghum means that pre-emergent control is often required. Metolachlor-based herbicides are frequently used.
• To reduce the potential damage to seedlings that come into contact with this herbicide, a seed safener (Concep® II) is required.
• Sandy/coarse/low organic matter soils are at a higher risk of herbicide damage.
• Many factors affect the level of exposure to and metabolism of metolachlor within the germinating seedling.
• Following mixing and application guidelines to get the most out of Concep® II

Key points influencing sorghum safety when using metolachlor-based herbicides

Factors increasing the chance of sorghum injury

• Rainfall or irrigation between planting and emergence wetting down to the seed zone, especially where waterlogging occurs.
• Light/sandy/gravel soils
• Germinating seedling under stress (e.g. waterlogging, cold shock, insect damage).
• Maximum application rates.
• Marginal soil temperature at planting.
• Defined planting furrows that with rainfall, act to concentrate herbicide over the crop row.
• Shallow planting depth.

Factors reducing the chance of sorghum injury

• High quality seed, treated with Concep® II seed safener.
• Concep® II seed safener applied within the past 18 months.
• Closing up of the planting slot to avoid herbicide coming into contact with the sorghum seed.
• Excellent crop agronomy.

To keep upto date with this publication use the following link www.grdc.com.au/TT-KeepingSorghumSafe

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• 1.51 mb Keeping sorghum safe 2016 northern (Web version) Tips and Tactics for keeping sorghum safe when using metolachlor-based herbicides.