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Optimising Your Pre-emergence Herbicide Application: A Guide for Autumn

News - 06.11.23

When it comes to pre-emergence herbicide efficacy this autumn, selecting the right combination of nozzle, adjuvant, and water volume is crucial.

When it comes to pre-emergence herbicide efficacy this autumn, selecting the right combination of nozzle, adjuvant, and water volume is crucial.

In this blog post, we'll explore key findings from Agrii trials and share insights to help you stay compliant with regulations while maximizing control over blackgrass.

Water Volume Matters

Achieving good coverage is a critical factor, and despite the temptation to use lower water volumes for efficiency, Agrii trials coordinator David Felce advises caution.

A trial demonstrated that a volume of only 100 litres/ha provided a mere 55% control of blackgrass. Increasing the water volume to 200lt/ha, coupled with DRT compliant nozzles, improved control to 83%, reaching an impressive 94% with non-compliant Defy 3D flat fans.

Support Bowsers for Efficiency

Many farmers are turning to support bowsers for in-field mixing, nullifying the time lost with greater water volumes. David emphasizes, "You are also gaining 28% more control."

Navigating Nozzle Challenges

Selecting the right nozzle is crucial, and the trial showed that a Defy 3D nozzle provided the best control at 93%. However, staying legal with buffer zone rules poses challenges. Farmers using DRT must observe buffer zones specified on labels, even with a 30m buffer zone from a water course without DRT. Three-star LERAP nozzles are recommended within the buffer zone, although they may reduce effectiveness. Agrii explores 4-star 90% reduction nozzles, potentially offering a compromise.

Chemistry Trials

Agrii conducted trials with Luxinum Plus (cinmethylin) + Orient (pendimethalin + picolinafen) using a tractor-mounted sprayer. Applying at 200 litres/ha with flat fan nozzles achieved over 90% control. Under DRT control, this slipped to 83%, but adding the adjuvant Backrow brought it back to 89%. Backrow normalises droplet size and enhances retention in the soil surface layer.

Water Volume Impact

Halving the water volume saw control drop to 55%, but adding the adjuvant increased it to 76%. The trial emphasizes that adopting DRT doesn't necessarily compromise control, as nearly 90% control was achievable with Luxinum Plus + Orient.


In the quest for effective pre-emergence herbicide application, understanding the interplay between water volume, nozzles, and adjuvants is key.

Our trials provide valuable insights, demonstrating that with the right combination, achieving optimal control over blackgrass is possible.

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