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Know your grassweed enemy, and adapt

News - 31.08.23

Understanding the Economic Impact

In a historic turn of events at Stow Longa, a winter wheat crop recorded the worst financial performance due to elevated input costs coupled with declining output values.

Colin Lloyd, Agrii's head of agronomy, emphasises the heightened risk of inadequate blackgrass control, illustrating the swing in margin over costs within feed wheat plots.

Weather Challenges and Grassweed Growth

Colin Lloyd notes that the weather last autumn, favouring grassweed growth, played a significant role in the challenges faced by growers. The wet yet warm conditions created a scenario where blackgrass thrived, hindering cultural measures and limiting the effectiveness of herbicides.

Adapting to Extreme Conditions

Steve Corbett, Agrii's head of trials, highlights the need for growers to develop systems capable of accommodating extreme weather conditions. Those who can adapt to the dynamic conditions, he asserts, will fare better in the increasingly tight economic climate.

Early Challenges and Cultural Measures

The forthcoming summer's rainfall is expected to prompt an early grassweed flush. Colin Lloyd suggests that this places pressure on growers to create a second flush before sowing, necessitating strategic planning for effective control.

Cultural Measures Unveiled

Agrii's long-term blackgrass trial at Stow Longa has been instrumental in investigating the value of cultural measures, including cultivation policy, establishment regime, cover crops, and crop choice.

Colin Lloyd underscores the variability in winter wheat yield based on cultivation methods, highlighting the impact on grassweed control.

In the trial, plots that were ploughed or recently ploughed (within the past two years) produced higher yields. Spring oats showed the least variance between cultivation regimes at less than 0.5t/ha.

Cropping Choices and Blackgrass Populations

The trial's results from harvest 2023 reveal significant differences in black-grass populations based on establishment regimes. Hybrid barley, traditionally effective in suppressing blackgrass, faced challenges in 2023 due to a cold spring, prompting considerations of alternative crops like spring oats.

In 2023, winter wheat with a heavy black-grass population returned a loss of £405/ha. The variance between the best and worst plots was about £1850/ha, highlighting the economic implications of effective grassweed control.

Unintended Consequences: Bromes and Ryegrass

Efforts to control blackgrass have inadvertently led to the rise of other grassweed species, notably sterile brome and ryegrass. Colin Lloyd warns of the risk of replacing one problem with another and highlights the impact of cultivation strategy on both grassweed control and overall yield.

Cover Crops: Learnings and Realities

Cover crops, long touted for their potential benefits, are assessed by Steve Corbett. He cautions against viewing cover crops as a panacea and underscores the need to define specific objectives.

While Westerwold ryegrass has proven effective against perennial ryegrass, cover crops are not a universal solution for black-grass problems.

Adapting Rotation for Ryegrass

Ryegrass, a formidable threat, requires similar cultural measures as blackgrass. Steve Corbett shares a successful case where addressing compaction and introducing spring barley effectively tackled a worsening ryegrass problem.

Bromes: A Manageable Challenge

While bromes pose challenges, especially sterile brome, ploughing emerges as a significant contributor to population management. Steve Corbett discusses trial results that showcase the effectiveness of ploughing in uplifting yields in brome-infested areas.

In navigating the intricate world of grassweed management, understanding the nuances of each species and adapting strategies to changing conditions become key ingredients for success.

The economic realities of yield variations and input costs underscore the importance of tailored approaches for sustainable and profitable crop management.

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