Our top tips for optimising efficacy of pre-ems this Autumn
Before cereal drilling gets well and truly underway, check out our top tips for optimising the efficacy of pre-ems – it’ll help you get timing and placement right for the best weed-free start.
If you’re battling black-grass, it’s likely you’re currently trying to hold your nerve and resist drilling cereals until at least mid-October. Afterall, we’re told it’s a low dormancy year (source: ADAS) so, we can expect repeat flushes in the presence of adequate moisture – something we’re not short of the past couple of weeks.
But, delayed drilling heightens the threat of suboptimal weather conditions that can chip away at the performance of even the strongest residual herbicide solutions/programmes, with the threat at its greatest the later we go in to the autumn.
So how do you reduce the risk and ensure it’s top-performing?
1. Add Backrow Max pre- and peri-emergence
Targets sprays for optimum coverage
Even spray coverage across the soil surface is essential to ensure maximum contact between germinating weeds and the herbicide. But spraying conditions typically become more catchy and gusty as we head in to the autumn, making optimum coverage often difficult to achieve. It also can result in some patches being over-dosed and others under-dosed.
Adding adjuvant Backrow Max significantly reduces the number of fine spray droplets smaller than 100 microns which are the most susceptible to drift. This increases the number of droplets in the optimum size range for improved deposition and optimum spray coverage of the soil.
Ultimately it reduces the chance of any untreated patches of soil for weeds to take advantage of.
Backrow Max significantly increases herbicide retention in the top 5cm of the soil
Above – Shows % pendimethalin in 0-5cm, 5-10cm & 10-20cm of soil following heavy rain event. Adding adjuvant Backrow increased pendimethalin retention in the top 5cm and reduced leaching lower down. Adding adjuvant Backrow Max was better still, increasing retention significantly.
Creates a stronger barrier to emerging weeds
Soil moisture is essential for residual herbicide activation and uptake. But with too much, all herbicides have the potential to seep out of the weed germination zone (top 5cm) in to the soil profile lower down, and this will result in a sub-lethal dose of herbicide being available to control germinating weeds.
The rate of movement depends on soil type, rainfall after application, and also chemical properties of the herbicide. But recent research has shown that even pendimethalin (with low mobility) can leach in wet soils putting effective weed control at risk – see graph left.
Backrow Max increases herbicide retention in the top 5cm of the soil, compared to herbicides applied alone. This ensures a longer more concentrated presence of the herbicide in the weed germination zone, creating a stronger barrier to emerging weeds.
It crucially maximises herbicide concentration in the weed zone for as long as possible and therefore gives you the best chance of controlling repeat flushes of weeds. Recent research has shown that Backrow Max provides even stronger herbicide retention than previously top-performing Backrow.
Protects crop safety
Heavy rainfall is not just a threat to efficacy, it can also risk crop safety by causing herbicides to leach out of the weed zone to the crop seed. Stacking residual herbicides heightens this risk.
As we saw in the graph above, Backrow Max increases herbicide retention in the upper soil profile, reducing leaching to crop seed (and groundwater) lower down.
Research in the Netherlands has shown that Backrow Max can reduce chemical leaching by as much 60%.
2. Apply within 24-48 hours of drilling
With adequate moisture, weeds will germinate within 24-48 hours of drilling, so for best results it is best to get your herbicide + Backrow Max applied as soon as possible after drilling so the herbicide barrier is in place before weeds start to germinate.
3. Optimise seedbed conditions
As residual herbicides work by creating a barrier in the soil to stop germinating weeds, it is important to minimise surface trash that may intercept the spray.
Also try to ensure soil tilth is firm, consolidated and clod-free. This will obviously depend on the cultivation method used, but for best results, try to optimise seedbed conditions. It will help to maximise herbicide contact across the soil, ensuring as much of the herbicide is in position where it is needed.
Need technical support?
As the weather gets more volatile, taking the steps above will help to improve herbicide reliability and safety.
For any questions or technical support, please get in touch with Will below – he’ll be happy to help.
You can also find out more about Backrow Max by downloading our Backrow Max booklet and FAQs.
