How to power residual herbicide efficacy and beat blackgrass

Power residual herbicides in sub-optimal conditions

In a favourable year, pre- and peri-emergence herbicides can deliver high levels of black-grass control, but the 97% control required to keep on top of populations, makes this very difficult to achieve.

Optimising herbicide contact with germinating weeds is a vital component of successful weed control, but when it comes to pre- and peri-emergence applications, it’s not as straightforward as you might think.

Residual herbicide performance depends on good application and soil conditions, with sufficient uptake in soil water by the roots and shoots of germinating weeds.

Herbicide placement and positioning in the soil is therefore vital but several factors threaten success.

The adjuvant Backrow helps residual herbicides to perform in suboptimal conditions, making it a vital addition pre- and peri-emergence to help mitigate the effects of poor application conditions, and very dry/very wet soils that lead to poor weed control and poor crop competition.

With double-digit increases in weed control on offer, Backrow could be extremely beneficial in winter crops this autumn.

What are the factors impacting herbicide performance?

1. Spray drift and clods lead to poor coverage

The performance of residual herbicides is heavily reliant on effective coverage across the soil surface to ensure full contact with germinating weeds.

In poor application conditions, spray droplets can drift off course leading to poor coverage, whilst cloddy seedbeds can hide weed seed from spray droplets.

Although drift reducing nozzles help to reduce drift, the coarser spray droplets do reduce coverage and this risks weeds escaping control.

2. Very dry and very wet soils lead to poor weed control

With a lack of soil moisture, weed control is reduced. Only in the presence of soil moisture can herbicides be absorbed into the roots and shoots of germinating weeds.

Residual herbicides need to be dissolved in soil water in the top  5cm of the soil to be available for uptake into the roots and shoots of germinating weeds.

In dry soils, herbicides with high adsorption tendency such as pendimethalin and prosulfocarb, bind even tighter to soil organic matter, rather than being dissolved in soil water.

With heavy rain and very wet soils, herbicides with moderate – high mobility such as flufenacet, can be washed below the weed germination zone preventing uptake into weeds.

Therefore in dry and wet soils the level of herbicide taken up by weeds is reduced, reducing the overall level of weed control.

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3. Heavy rain threatens crops safety and groundwater

To be effective and safe to crops and groundwater, residual herbicides must bind to soil colloids (clay, organic matter) with only a small amount remaining in solution.

With excessive rainfall, herbicides that are even moderately mobile can be lost, particularly in light soils, and there is a risk of heavy rain washing residual herbicides to the seed which can result in crop damage and reduce crop competition.

How can residual herbicide performance be improved?

Protect crops and beat weeds with Backrow

Backrow is fast becoming a vital performance adjuvant for pre- and peri-emergence herbicides to work at their best.

Backrow powers residual herbicides in sub-optimal soil and application conditions by reducing drift and by optimising herbicide and moisture retention in the top 5cm of the soil.

The resulting improvements in herbicide coverage and uptake into weeds are crucial benefits for growers to protect crops and beat weeds for the best start.

What are the key advantages of Backrow?

• Improved weed control in poor application conditions
• Improved weed control in very dry and very wet soils
• Improved crop safety in wet soils

How does Backrow improve weed control in poor application conditions?

Backrow improves herbicide coverage of the soil in suboptimal spraying conditions, leading to an increase in the overall number of weeds controlled.

By creating the perfect size spray droplets for pre- and peri-emergence herbicide applications to work at their best, Backrow reduces the number of fine spray droplets prone to drift and increases the number of droplets in the optimum size range for better spray coverage of the soil.

This improvement in coverage increases the number of weeds that come into contact with the herbicide at germination, resulting in a higher level of weed control overall.

How does Backrow improve weed control in dry and wet soils?

Backrow increases herbicide uptake in dry and wet soils, improving the overall level of weed control that can be achieved in suboptimal soil conditions.

Backrow helps to retain moisture in the top 5cm of the soil – in dry soils this higher moisture means more of the herbicide can be available for uptake into weeds.

Backrow retains moisture and herbicides in the top 5cm of the soil, increasing herbicide uptake into weeds.

By increasing herbicide retention in the top 5cm of the soil, Backrow also improves herbicide uptake in very wet soils, instead of herbicides being washed below the weed germination zone where uptake would be prevented.

How does Backrow protect crop safety in wet soils?

Backrow improves crop safety by minimising herbicide movement down to the seed and emerging shoots, or worse still, leaching to groundwater. By helping to retain herbicides in the top 5cm of the soil, Backrow protects crop safety and groundwater in very wet conditions. 

What difference will Backrow make to my weed control?

In Agrii trials over the last 11 years (2009 to 2020), Backrow has improved the control of various grass-weeds by an average of 9.5% – this is the mean of 46 comparisons either pre- or peri-emergence, and with a range of residual herbicides applied in cereals. 

The highest increases in weed control will be achieved in suboptimal conditions.

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