16 December 2000

Latecomers thrive

The A-team, on a mission for optimum yield from cost-effective inputs, is making plans for the spring. Tom Allen-Stevens joins them in the trial plots.

HEREs been a turn of events for the intrepid A-team: their late-drilled plots at Boxworth are looking decidedly more healthy than those drilled earlier. Seed rate and drilling date were two of the variables on trial, and crop physiology expert Roger Sylvester-Bradley admits it hasnt quite turned out as expected: "The early, low seed rate plots are going to need some careful management throughout the rest of the year."

By contrast the later-drilled plots have established well. But John Spink, new recruit to the expert team and another physiology specialist at ADAS, points out that the sparse early sowings may not be typical of a commercial situation: "The early plots were surrounded by stubble when they were drilled, and the new sowings attracted all the local slugs. Despite frequent pelleting, the edges of the plots especially have suffered severely."

Its early in the season, but plans are already being put in place for early spring remedial work. With heavy rainfall adding to their worries, Dr Sylvester-Bradley recommends most growers should consider early mineral N testing, to gauge how much early N may need to be applied. "Light soils leach anyway, but medium soils are likely to have leached to the extent a light soil would in an ordinary year. Mineral N will be very difficult to estimate in heavy soils, so its especially important to test these."

Normally he tests down to a depth of two feet in the winter, and three feet in the early spring, but this year he recommends going the full depth in December: "You need to get an idea of how much N there will be at four to five feet next summer, and testing to three feet now should give us an idea."

But N found this deep will do little for tiller establishment – testing to depth has more to do with ensuring you have ordered enough fertiliser overall. "Its important not to scrimp and save. If youre ordering fertiliser at todays prices, you need nerves of steel."


The first priority in the spring will be to nurture backward crops, aiding shoot development and tillering. The crops most in need of attention will be those that have established poorly, like the early-drilled, low seed rate plots at Boxworth. These will receive 40kgN/ha in mid-February. A watching brief will be kept on other plots, even though they currently look all right; if they turn yellow and begin to suffer, theyll receive a similar dose in mid-February to early March.

Many growers will find their early-sown plots may not require early doses of N. "If youre looking at populations of 300-400 shoots/sq m already, early nitrogen may not be so necessary," advises Mr Spink.

Up in the blackgrass plots its a similar picture: the later the better. The site here is infested with resistant blackgrass, and two different cultivation methods are under trial, along with sowing date.

"Very little blackgrass emerged pre-drilling in the early-sown (25 September) plots, which is why its all come up in the crop," reports ADAS weed expert James Clarke. "Im much happier with the later-drilled (15 November) plots, even though they havent yet emerged."

Now its up to the post-emergence sprays. They were applied at the beginning of November on the early plots, but will have a job to tackle the high populations – around 500 blackgrass plants/sq m. Any remaining blackgrass will now be tillering, so again will be a challenge for chemical control, believes Mr Clarke.

A good kill was achieved with pre-emergence glyphosate in the later plots, which has removed much of the pressure, says Mr Clarke. But growers in a similar situation cannot afford to relax. Spraying should still be a high priority, even if theres still drilling to complete, and must not be left till spring.

"Keep up the pressure, particularly in a thin crop, because the blackgrass will be good at colonising gaps. Take the earliest opportunity to spray, even if thats in a frost. A good post-emergence mixture would now be Hawk (Clodinafop-propargyl + trifluralin) and Lexus (flupyrsulfuron methyl)."

He warns growers to check label recommendations when spraying in a frost – frost heave can allow shallow roots to take up damaging levels of residual herbicides. Complicated tank mixes should also be avoided. Novartiss Chris Rowsell confirms that Hawk is cleared for use and is active at low temperatures.

"Set priorities by likely level of control and first spray those fields where a good level of control is expected (ie where blackgrass is still pre-tillering) or essential. Generally early-drilled crops warrant earlier spraying, with pre- and post-emergence applications to later drilings being lower priority," says Mr Clarke.

Action plan

&#8226 Monitor establishment

&#8226 Set total N levels (after judging N supplies and leaching losses)

&#8226 Begin to formulate early nitrogen and growth regulator strategy

&#8226 Prioritise order of field needs

The A-teams mission:

The team:

Bill Clark, ADAS national cereal pathologist

James Clarke, ADAS arable technical manager

Roger Sylvester-Bradley, principal research scientist, crop physiology

John Spink, principal research scientist, crop physiology

Novartiss Chris Rowsell and Colin Mills are supplying extra technical input

The objective:

To achieve the optimum yield from a cost-effective input regime which would give the UK grower the maximum margin at world market prices

The location:

Trial plots at ADAS Boxworth and at Scottish Agronomy in Arbroath

The variables:

2 x seed rates, 2 x drilling dates, 2 x varieties. At Boxworth the trials are repeated on a site heavily infested with blackgrass, with two cultivation regimes

The criteria on trial:

Weed control, disease control, lodging prevention, canopy management and nutrition