Article taken from Farmers Guide, October 2018
Achieving an even coverage of the seedbed when applying pre-emergence herbicides is vital to ensure the chemistry works as effectively as possible.
One of the most important factors governing this is the number of droplets produced by the nozzle. We need to paint the soil evenly and, within reason, the more droplets we can produce, the more effectively we can do that.
Using twin caps fitted to a single spray line enables us to double the number of nozzles, and therefore droplets, for the same water volume, and I would recommend a minimum of 200-litres/ha when spraying black-grass.
Nozzle know-how
The twin caps have back-to-back nozzle apertures. Billericay twin caps are already angled forward and down, so two VP 80 flat fans can be used. Hypro Twincaps are inclined 30 degrees forwards and backwards, but fitting a Defy 3D (80-degree) nozzle to the rear-facing aperture produces a near-vertical fan.
Using twin caps mimics a twin-line set up, which has given excellent results in our trials. On heavily infested black-grass land in Northamptonshire, for example, applying full-rate diflufenican and flufenacet in 200-litres/ha of spray at 3 bar through twin lines fitted with blue 80-03 flat fan nozzles, carried 50cm above the ground, gave 90 per cent control. A single line set up of 80-04 flat fans, alternating forwards and backwards, gave just 80 per cent control.
It really is worth spending the time to get application right. Too many people look to cover the ground quickly using around 100-litres of water/ha applied through low-drift nozzles so they can keep going in marginal conditions, but at what cost?
Several of my growers have now adopted the twin cap technique, and they believe they are seeing a difference.
Whatever technique is being used to apply pre-ems, I’ll be recommending Remix, a long-chain hydrocarbon application aid that reduces spray drift and produces a more consistent droplet size. It also keeps the chemistry in the surface layer for longer to optimise weed control and reduce seedling damage.
Significant uplift
Extensive trials over the past 10 years have shown Remix increases black-grass control from a typical pre-em stack by 11 per cent, a very significant uplift, for a few £/ha.
Remix consistently outperforms competitor products. In the season just gone, for example, Remix and a product which claims to be the same were applied in a tank mix with pre-em Liberator (diflufenican + flufenacet) at 200-litres/ha through flat fan 04 nozzles, at three sites in the East of England.
Remix gave an average 7 per cent uplift in black-grass control, and maintained a 2 per cent lead overall under four different post-emergence follow-up treatments. That could make the difference between achieving the 98 per cent control we need to reduce the black-grass burden, or not.
I’ll also be keeping a close eye on grass weed control in oilseed rape. A combination of low-dormancy black-grass and the reduced cultivations when establishing OSR crop this summer means there are likely to be a lot of grass-weeds near the surface that will be germinating readily.
As usual I’ll be starting early, using clethodim (as in Centurion Max) by the end of September, before following up with carbetamide (Crawler) in bad situations in October and propyzamide (Kerb) in all fields when conditions are cool enough to optimise activity. We cannot afford to wait and expect Kerb to kill large, well-tillered black-grass plants – that is a recipe for disaster.
Centurion Max can no longer be applied on any variety of OSR after 15th October. We must also observe stewardship requirements on carbetamide and propyzamide if we want to preserve them for future use. Please do check all requirements carefully before application.
Rob Sheets is an agronomist with Agrovista, based on the Northamptonshire/Cambridgeshire border (robert.sheets@agrovista.co.uk)