Host farmer Andrew Williamson is continuing to keep a close eye on black-grass despite there being relatively little on farm.
The approach predates the Bayer Task Force in Action Project but sees the extra advice as invaluable in honing the farming system. Black-grass counts in the focus field in 2019 were 2.2/m2 on average but with some as high as 30 in bad areas. Likewise, the seedbank analysis from NIAB showed approximately 200 seeds/m2 which is low compared to farms further east but shows there is potential.
“Farmers in lower pressure situations like ours, see no black-grass from the sprayer and think the field is clean,” says Mr Williamson. “But we go back and walk the tramlines to rogue and there are always some plants. We know that we are one bad season away from a much worse problem.”
The late drilling formula used on many farms for black-grass control does not work so well according to Mr Williamson. High silt content soils which are prone to slumping and a wetter climate than many arable farms are the key reasons why.
“I understand the case for late drilling for black-grass and BYDV control, I know it works in other parts of the country but on this farm and soil type it has never worked well. But black-grass is in patches, so I prefer the whole field to be drilled at the economic optimum for wheat and then deal with patches by roguing or even spraying out, it’s better than having a whole crop poorly established or not drilled at all like last autumn.”
However, Mr Williamson is prepared to take a wide range of other steps to control weeds. “There used to be a very prescriptive approach to cropping but now it is much more flexible. It’s a bit more awkward logistically but it is better for black-grass control. If a field has black-grass we always combine the bad area last and then blow down the combine – irrespective of if there’s rain forecast and so on. On owner-operated farms we can make that decision but on larger units with a business structure it’s slightly harder to justify stopping a combine in the middle of a good day for harvesting.
Winter wheat is grown every four years in a rotation of oilseed rape, then wheat, followed by two spring crops. “We have started growing more spring crops because of the problems with weeds including black-grass. Double spring cropping means that we get good weed control before two crops where it is harder to control. Especially because we tend to drill wheat by the first week of October,” says Mr Williamson.
The focus field came out of wheat in 2019 so last season was the first of two spring crops. Initially the plan was to grow oats; however, in spring, the decision was made to switch to barley to ensure there was sufficient crop to meet a malting contract.
Ahead of the spring crop, Mr Williamson aims to use cover crops to protect the soil over winter. The principle is great but frequent late harvests in Shropshire make it a challenge to get it right.
“Last year we drilled phacelia, vetch, buckwheat and spring beans on 30 August, which is too late. Only the beans established but by spring there was quite a bit of cover along with some cereal volunteers.” As the crop was fairly thin, it was sprayed off and drilled 3 days later at the end of March.
“A lot of the benefit of a cover is below the surface, it didn’t look much but this cover did help with the rooting and did its job of protecting the soil and keeping it biologically active after a terribly wet autumn and winter,” says Philip Wright. Looking across the whole field he thinks that barring a wet harvest, compaction is only likely to be a problem on headlands.
In the 3ha area of field with bad weed problems, Mr Williamson decided to use a robust pre-em programme in the barley crop with Trooper (pendimethalin + flufenacet) followed by Herold (flufenacet + diflufenican). Despite clearly affecting black-grass and other weeds it has also affected the crop raising questions about the value of herbicides in spring barley.
Crop walking and satellite imagery from FieldView both show a clear difference in crop condition between the treated and untreated areas.
“Using herbicides in spring barley crops is an interesting discussion because we know that pre-ems do affect the crop,” says John Cussans. “We grow spring barley because it is naturally competitive so does it make sense to hinder that natural advantage with a herbicide? So, we need to find out do you get more control from natural competition or the herbicide.”
The plan is for another spring barley crop because the malting contract has been renewed. Once again Mr Williamson will use a cover but not try and force in a multi-species mix too late in the year. If he can drill by mid-August, he will use the same mix as last year. Any later, and he will switch to just spring beans as they proved successful even in last year’s very wet autumn.
Cover crop growth and establishment will be an indicator for soil condition. Checking surface cover and rooting should make it fairly straightforward to find areas of the field which have poor soil structure. The idea is then to use a sward lifter to gently loosen through the growing cover and then allow the roots to finish off the job ahead of spring. There will also be a strip left without any cover crop as a control to get a better idea of any benefits.
To look at the questions raised by the 3ha are that was treated this season, there will be a herbicide trial next season. It will look at no treatment, a single product such as 0.3 l/ha Liberator (flufenacet + diflufenican) and a two product sequence similar to what was used this year.
The aim is to examine not only the effect on black-grass but also crop development so tiller number, ear size and canopy condition. To add more detail to the data, the trial will be replicated at the Task Force in Action site in Abbot’s Ripton.
Understanding your seedbank is an important step in gaining a critical advantage on black-grass control this season. Seed return from the previous crop, cultivation techniques, and the quantity and type of weed seeds at different depths, all influence your integrated weed management strategy.
NIAB weed control specialist, John Cussans, talks about the seed bank sampling work they have been doing as part of the Bayer Black-Grass Task Force initiative.
Black-grass control does not start with the pre-emergence herbicide programme. Doing everything possible to reduce the weed population before you drill the crop is key, and it means making good management decisions right from the off.