Arable News

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Agronomy update

Now is the time to be assessing maize crops ahead of harvest.

Correct timing and application of cereal pre-emergence herbicides and assessing maize for harvest are on Agrovista agronomist Craig Green’s checklist.

Stale seedbeds have generally been working well this season thanks to August showers that kept soils damp near the surface.

Weeds have germinated rapidly after a light cultivation, though black-grass, a key target for many growers, has been proving less willing to show on some farms, says Norfolk based agronomist Craig Green.

“Germination has been a bit sporadic in places,” he adds. “I suspect it’s due to lack of moisture on fields that largely missed the showers rather than being a dormancy issue.”

Many growers have achieved at least two chits since harvest, so Craig is more relaxed about talk of early drilling.

“Plenty of people have been talking about making a start on wheat, taking the view that if the crop is in the ground they can manage it, whereas if we get a wet week or two they may not be able to get back on.

“It’s a question of really keeping on top of crop management. Black-grass is the real worry, and pre-ems only have a limited life, so we need to get the best out of them we can.”

It is imperative to roll immediately after drilling, he maintains. “A cloddy seed-bed is no good to man or beast. Although it’s been a very good year for cultivations some clods are being pulled up and they need to be rolled straight away.

“Ensure the sprayer is tight behind the rolls – this might be a hassle but you will see a big benefit in terms of pre-em efficacy. If Avadex (tri-allate) is to be applied put it on behind the roller and book a contractor in plenty of time.”

It will also pay to order early, says Craig. Flufenacet, the cornerstone of every black-grass pre-em programme, is in short supply. “There won’t be any fresh supplies this side of Christmas. Avadex is also getting hard to find. Everyone seems to want it.”

He favours Trooper (flufenacet + pendimethalin) at 2.0 litres/ha + 0.3 litres of Herold (diflufenican + flufenacet) where black-grass is a problem. This puts down 240g of flufenacet, 600g of pendimethalin and 60g of diflufenican. Adding 120g/ha of Absolute (diflufenican + flupyrsulfuron) in winter barley will help make up for the lack of post-em options.

Where black-grass is absent, he’ll use lower rates or switch to PicoMax (pendimethalin + picolinafen) plus diflufenican to control meadow grasses.

Product choice is only half the story, says Craig. “The other half is application. Agrovista trials this season showed control ranged from 10-95 per cent or more, simply by changing the application.

“Be sure to use the right nozzles – alternating forward and vertical VP 80-03 flat fans along the boom and using 200 litres of water/ha worked well. If you can, use a boom height of 50cm. I’ll also recommend Grounded, which reduces drift and helps to bind the herbicide actives to clay and organic matter, keeping them in the surface layer for longer.”

Compaction indicator

Maize crops look very well and are about two weeks ahead of normal, says Craig. “There’s not been much eyespot about – many second crops went in to ploughed ground. It’s also been a good growing season – it looks like a good year for yield.”

Maize is a good indicator of compaction, so it will pay to note areas of uneven growth and check these after harvest. Soils are likely to be dry enough at depth to correct the problem, he advises.

Ensuring maize is mature at harvest will be key. “Harvest too early and you’ll be carrying a lot of water,” he warns. Once cobs can no longer be dented with a thumbnail crops are probably ready, but stems should also be wrung out to see how much water is in them.

“There is a free app now available from Limagrain for all Apple devices to help growers assess crop maturity,” says Craig. “And make sure your contractor is booked – they are going to get very busy before long.”

Oilseed rape growers should continue to monitor flea beetle damage and spray cypermethrin at first signs of damage. “Follow up as necessary until plants are big enough to withstand the pest – four true leaves – and growing strongly,” Craig advises.

“I’ll also recommend foliar phosphite to encourage rooting on early-drilled crops and foliar nitrate to encourage later-drilled, slower moving stands to put out true leaves.”

 *Craig Green is an agronomist with Agrovista, based at Great Ellingham, Norfolk ([email protected]).

  • Written by: Farmers Guide
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