New trials sites provide tough test for grass weed management strategies

Article taken from the Agronomist & Arable Farmer


Resistant ryegrass has become a big problem for many growers in Yorkshire and further up the east coast to the borders, and across into Shropshire and other areas where mixed farms predominate, says Agrovista technical manager Chris Martin.

"It has become their number one grass weed.  It is often a worse problem than black-grass in these areas - it is no exaggeration to say it is like silage in some fields."

The new ryegrass management trials, on land farmed by G & M Westgarth, will build on other grass weed work being carried out by Agrovista, including trials on meadow grass in North Yorkshire and, for the past three years, on resistant black-grass at heavy-land sites in West Yorkshire and Northamptonshire.

Like the black-grass sites, the ryegrass work will investigate a range of cultural and chemical control methods to allow growers, whose land is affected by the weed, to continue to operate profitable cereal-based rotations.

Severe test

The trial field will provide a severe test for control strategies, Mr Martin said.  "It contains very difficult ryegrass - the chemistry set has been failing for the past few seasons, and it has now become almost impossible to grow a winter wheat crop on it."

For the purposes of this year's trial, the main part of the field has been sown to second wheat KWS Gator.  This will be treated with a matrix of 90 different chemistry combinations.

"We are using nine different pre-ems, including the best existing actives plus potential new residual chemistry," said Mr Martin.  "All of this will be applied with and without Avadex, and will be overlaid with seven additional early post-emergence residual options."

Most of these autumn treatments will then be over-sprayed with contact chemistry, both in the autumn and spring, to assess additional efficacy, he said.  "We believe this makes the trial the most comprehensive ryegrass trial ever seen in the UK."

As this is the first year of the project, only one set of results, from pre-emergence residuals, are available, said Mr Martin.

The untreated plots indicate the severity of the problem, containing 870 ryegrass plants/m².

Best control before over-spraying has come from Trooper (flufenacet + pendimethalin) at 4 litres/ha together with Defy (prosulfocarb), also at 4 litres/ha. 

"This left 95 plants/m², which is a good start in anybody's book," said Mr Martin.

"However, it is expensive and could be quite hote on the crop. 

"Although it produced a better result than the more commercial 4L:2L rate, it will be fascinating to see how these and other pre-em treatments influence outcomes after the follow-up treatments are applied."

Cultural control options

A range of cultural control options is also being trialled across the site.  These include various cultivations, different drilling dates and cover crops, in conjunction with the various chemcial treatments.

"The farm standard is based on a non-inversion tillage programme, using a Great Plains DTX tine-disc cultivator as the primary cultivation tool followed by a pass with an X-Press disc harrow," said Mr Martin.  "The crop was drilled in September, usring Horsch Pronto cultivator drill."

The second programme is the same as the farm standard, but drilled in early November.  "You would not usually do this commercially - we know how risky November sowing can be in any part of the country, but especially this far north," he said.

The third, and last, autumn programme is also based on early November drilling, but modified to make it a more reliable commercial option.  It is based on the same cultivation elements as the farm standard, but follows a black oat and vetch catch crop.  Additionally, the crop is drilled using a Vaderstad Rapid, with the cultivation elements disengaged.

The idea is to use the cover crop to suck moisture out of the ground, so the drill can travel, said Mr Martin.  "Provided you get six to eight weeks of growth, the cover crop should do its job and you should be able to establish the wheat."

Using the Vaderstad this way mimics a direct drill, but without the expense - many growers are already using this or a similar drill, he added.

The disc-only drilling action minimises soil disturbance, which reduces ryegrass see germination and makes for an even more weatherproof system, he explained.

The cover crop is sprayed with glyphosate a few days before drilling.  "The field may not look pretty after sowing, but it appears to have been an effective strategy this season," said Mr Martin.

"The idea is to establish the cover crop as early as possible, probably after barley or oilseed rape this far north, then keep an eye on the forecast and spray off and drill once the weather looks like breaking."

Spring cropping

Three spring cropping programmes are also being evaluated at the site: non-inversion spring barley following fallow, non-inversion spring barley following a black oat and vetch cover crop, and ploughing ahead of spring barley, both with and without an over-winter cover crop.

"With all these programmes, we want to move as far away as possible from the optimum germination periods for ryegrass," said Mr Martin.  "That means avoiding August/September and April, while maximising the competitiveness of the crop.

"To do this, we need to adopt the optimum chemistry, backed up with appropriate cultivation measures.  We think that will mean delayed drilling, which is pretty scary up here, but our black-grass trials' experience elsewhere has shown how effective cover cropping together with appropriate cultivations can be in widening the drilling window on heavy soils."

Mr Martin added: "Early results look promising."

Grower will be able to assess the results for themselves at a series of open days next year, and beyond.


12 January 2017

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