Article taken from Arable Farming, August 2017.
As combines start rolling across the region in earnest, it's a good time to reflect on the past year's cropping. Once again the unseasonable weather has had a major effect on our fortunes and on the back of that it's looking like a variable harvest.
On the one hand, well-managed winter crops on well-bodied land look like they will yield well, while on the other some late-drilled spring crops which suffered badly from the draughty Conditions in April and May look like they may be a salvage operation.
Variability in grass-weed control across the region has really struck me this season. Every day through-out June and early July, more and more yellow patches appeared in fields where crops had been prematurely destroyed with glyphosate to reduce further seed return from grass-weeds.
Autumn residual herbicides generally worked well but once again application was crucial to maximise full performance. I've seen on many occasions this year where the same product applied on the same day has either worked well, or barely appeared to work at all, and virtually every time we drill down into why, the difference is how the product was applied.
The key for maximising performance of residuals is to 'paint' the soil and the key to this is to produce as many droplets as possible. This can be achieved by using a higher water volume, while not compromising droplet size, and the finer droplet you can achieve on the day of spraying the better.
To emphasise this, with the same water volume, for every one coarse spray quality droplet measuring 400 microns in diameter, you would produce 64 droplets of a fine spray quality, each measuring 100 microns in diameter. In practice there are several ways to achieve this. Reducing forward speed is a good start, delivering more water while maintaining droplet size. This also helps aid boom stability allowing you to keep the boom as close to the target as possible, which is also key in reducing drift. If the practicalities of getting round the acreage with limited spray days do not allow a reduction in forward speed, use twin lines, or forward and down angle caps (not backward as spray becomes too drifty at practical forward speeds and boom heights).
Application trials
In many years of extensive application trials with Agrovista, a twin cap with an SO-degree flat fan nozzle angled 30 degrees forward and 110-degree flat fan nozzle straight down have consistently given the best results, and these results are clearly being repeated in the field. The addition of an application aid such as Remix to residual herbicides has also proved beneficial in improving coverage and due to its unique positive charge enabling it to bind to soil colloids such as clay particles and organic matter, it keeps the product in the zone of activity for longer. Not only does this improve the persistence of the herbicide, but also reduces any potential crop damage by reducing chemical coming into contact with emerging seedlings of the crop, which is becoming an increasing concern· as we stack more and more residual chemistry in this fight against grass-weeds.
The final part of the application jigsaw is seedbed preparation, which helps maximise product performance and minimise crop damage.
Agronomist facts
Chris Martin is a technical manager for Agrovista, based in the north east of England. His role is to provide technical advice to growers over an area extending from Lincolnshire to Scotland. Prior to this, he was an agronomist with the company for 15 years and continues to provide agronomy advice to a number of growers producing combinable crops in the Scotch Corner area.