BGTF Podcast: Cultivating successful black-grass control

Read the transcript of the podcast below.

Dr. Black Grass:  Hello and welcome to episode 4 of Dr. Black Grass on air. This show is about cultivation and the use of glyphosate to make stale seed beds and we're also going to touch on crop selection. Once land is clear after harvest, it is the best opportunity to encourage black grass to chit and then be destroyed. Glyphosate plays a big part is most people's stale seed bed programs, but as with all herbicides, it needs to be used with consideration for the risk of resistance, so that it can remain effective for years to come.

Earlier this summer, WRAG - The Weed Resistance Action Group - of which Bayer is a member, issued guidelines on the responsible use of glyphosate. At Cereals, I've caught up with James Clark, WRAG Chairman and ADAS researcher to outline what these new guidelines mean for UK farmers.

James Clark: We believe that the practices people are adopting now, which is basically a very large number of applications of glyphosate, reliance on glyphosate in the gap between harvest of one crop and cultivating and drilling the next, and coupled with that, some low use rates, we believe that many people are adopting an approach which is creating a higher than acceptable risk.

Dr. Black Grass: Okay, and have other countries had this problem?

James Clark: Yes, there is, globally, at least 31 weeds that are resistant to glyphosate, so weeds can develop resistance to glyphosate. That is a given. The question is, can we make sure that people have got information available to them that prevents that resistance from developing in the UK population? That is why we're issuing these guidelines.

Dr. Black Grass: What are the best steps to prevent resistance developing?

James Clark: We have a very simple message, we have an 8 word message which is simplistically: prevent survivors, maximize efficacy, use alternatives, and monitor success. Then on the AHDB website, you can access, or directly from them as hard copy, a 2 page guidance document that gives you more information on each of those together with the higher and lower risk factors that underpin those, and that will also give you access to, or you can access it directly from The Weed Resistance Action Group website, an 8 page document. The first 2 pages are identical technical content, the other 6 pages give much more information, particularly on how to maximize efficacy, more information on rates of use, more information on interaction with other cultural controls, together with more of the story of why resistance has developed elsewhere in the world and why we're presenting this message now.

Dr. Black Grass: Will control increasingly depend on cultural methods rather than chemical applications?

James Clark: It's a partnership between cultural control measures and herbicides, whichever they are. It's also a partnership between herbicides whether it's the non-selective between crops and the pre- and post-em herbicides that you'll use within crops. Each of them are helping each other in the sequence.

Dr. Black Grass: Lots of people who are dealing with black grass, they rely on repeated chitting, and then spraying off with glyphosate. Would you say this is a high risk strategy?

James Clark: We believe that repeated chitting is a good approach, it's whether you need to achieve that through multiple applications of glyphosate. We believe that multiple applications, especially at low dose of glyphosate, presents part of the higher risks that are involved in this, so the question is, when do you use it sensibly and we're suggesting that a maximum of 2 applications should be a manageable risk.

Dr. Black Grass: Okay, and if you want to get more chits than that, what control methods could you employ instead?

James Clark: You could cultivate, you could leave the soil undisturbed to maximize moisture, and obviously a lot of these plants need moisture to germinate. You need to choose the system for the season so that you maximize the amount you get rid of. But equally, if you allow them to grow, and then you get a good clean kill followed with cultivation, then you're doing another very effective way of reducing that overall population, and reducing the pressure that you're then putting on your subsequent crop herbicides.

Dr. Black Grass:  Cutting back to only 2 applications per year may be a challenge for some people, but introducing more mechanical processes to control black grass will be of benefit to all farms. One of the leaders in integrating chemical and cultural control are Claydon Drills. I spoke to Spencer Claydon about how they use cultivation and drill technique to reduce dependence on non-selective herbicides.

Spencer Claydon: Okay, well we offer a unique system. The Claydon System consists of a direct drill and before that, the straw harrow. The straw harrow is probably the most important tool when it comes to controlling grass weeds and also volunteers and weeds within the crops. We use the harrow very shallowly, it's only cultivated at around about 2 centimetres deep, it gets the weed seeds mixed into the top of the soil, into the moisture, they then begin to grow. You can actually go back with the straw harrow and hoe out a lot of the little seedlings once they've hatched, very, very quickly, very cheaply, around a litre of fuel a hectare, covering a lot of ground. For instance, a 7 1/2 metre straw harrow will travel at around about 25 kilometres per hour, so it's extremely cheap, extremely effective to do the job, and as I say, if you have the window of opportunity, you can go several times with it to actually hoe out the small seedlings once they've hatched.

Dr. Black Grass: Okay, and how many times would you typically go into a crop to harrow?

Spencer Claydon: Well it very much depends, for instance, if you're following with oilseed rape and growing an oilseed rape crop, you perhaps wouldn't have time to actually do any harrowing, you'd just go straight in and you'd deal with it with the chemical controls which are available. For instance, if you were going in after oilseed rape with a wheat, you'd have a large time window and in that time window you can go through with the straw harrow several time, you can get the cotyledon rape going as well as the grass weeds and everything else, you can hoe them out and kill the food source of the slug as well at the same time, and actually get a very effective control of the volunteers, of the weed seeds and everything else with a very cheap system just to run across.

And you can use it, of course, before direct drilling or indeed, if you're cultivating, you can use it before that to get a control before you go mixing the whole soil profile from top to toe and integrating those weed seeds if you haven't controlled them. We recommend spraying off with a chemical like glyphosate before you do the cultivations and such like, and actually getting a kill for a stale seed bed beforehand rather than actually going through and just mixing them from various levels and having the weeds coming at various points and at different growth stages.

Dr. Black Grass: So obviously you think straw harrowing is very important, what other things did you think about?

Spencer Claydon: Okay, we offer a various range of options on our drills. The standard set up is a strip seeding set up, so we're only disturbing where the roots are going to grow the plant, and where the seed is being placed. With our machines, all of the wheels run on the uncultivated ground, or run in front of the tines so they’re at constant depth the whole time. We actually level with the chassis of the drill and we bring the soil to the seed, and not the other way around, so we're actually levelling every time you use the drill.

Dr. Black Grass: Does that level seed bed then help with sort of anything you follow it with, pre-emergence herbicides and so on?

Spencer Claydon: Definitely, we find that with pre-emergence herbicides, it's very important to keep the moisture within the soil and by going directly into the stubble, as we mainly do with the drills, you actually have more moisture in the soil to allow the herbicide to travel within the soil. Also, we find that having a level field stops it from having ruts in which you then end up having water building up there and potentially that's where the grass weeds start within those dips and hollows within the fields.

Additionally, as well, because the drills go straight into the stubble, they create a nice fine tilth, and not creating big lumps and clods in which you'll find that the grass weeds are hiding underneath them and not chitting at the right time.

Dr. Black Grass: Thanks a lot Spencer, so cultivation and drill technique play a huge role in limiting Black Grass, but what about the choice of variety that you put in the ground. How much of an effect does this have? I briefly spoke with Claire Leaman of NIABTAG at Bayer's Long Sutton Open Day, about how much control you can get from a more competitive variety.

Claire Leaman: Black grass just seems to ... whatever crop it's in, it grows just out the top of it, doesn't it? I think when you're dealing with black grass there's a lot of cultural measures you can take that have varying input into the control. Competitive varieties might be one of them but the impact is relatively small, that you get, and there's things that you can change much more easily like seed rate that would have a bigger impact, so probably you ought to choose a variety that you really want based on the agronomic characteristics and the end market and then make any other changes with that variety and not base your whole variety decision on competitiveness.

I was talking to someone on Tuesday saying that they've never seen so many out in the fens where black grass is only just really becoming an issue isn't it, never seen so many rogueing teams pulling black grass. So the message has obviously got through that if you've just got a small amount, get it out.

Dr. Black Grass: So variety choice will help, but won't make a massive contribution. But what about the use of alternative crops? We don't have time today to go through all the potential options, but of course one of the most popular crops is oilseed rape. I spoke with Darren Atkins at Bayer CropScience at the Long Sutton Open Day as well, and he gave a quick outline of what you need to look out for when using this crop.

Good afternoon Darren.

Darren Atkins: Good afternoon.

Dr. Black Grass: Lots of people use oilseed rape as a break crop, and obviously their grass weed control would be one of the factors in making that decision, what are the possible benefits and the risks of using oilseed rape in this way.

Darren Atkins: Oilseed rape can be a very useful management tool in grass weed management, potentially you've got access to different chemical groups which are propyzamide and carbetamex, and these have very useful residual chemistries but they can be subject to weather conditions, they need cold and wet conditions to work at their maximum. Used at the correct time they are very useful but it is always a good idea to go in and check levels of control in the spring because often grass weeds can be hidden below the oilseed rape canopy.

Dr. Black Grass: Okay, and is there anything you can do with variety choice and sowing date with oilseed rape?

Darren Atkins: Well, oilseed rape is a very vigorous crop when drilled in the right conditions so using a vigorous autumn establishing variety will be useful. In a lot of cases, hybrid varieties do show more autumn vigour than open pollinated varieties.

Dr. Black Grass: Okay, and you mention in the spring you need to check black grass levels in the sort of canopy itself, if you've got higher than ideal levels, what steps can you take sort of looking forward to harvest and maybe the following autumn establishing a wheat crop?

Darren Atkins: Well you're got two options. If the levels of grass weeds in the bottom of the canopy are extremely high, you've got the option of spraying that section of the crop off, so you're not getting seed return. But oilseed rape is harvested generally quite early so you do get several chances to put stale seed beds in before drilling wheat, so the early harvest and delayed drilling will potentially allow two or three stale seed beds to be produced to get the seeds that shed to germinate and be sprayed off with glyphosate before drilling of wheat.

Dr. Black Grass: Thanks a lot Darren.  So we’ve heard of quite a few different measures you can take to build into a black-grass control programme and if you’d like more information and advice about putting together a programme for your farm you may want to take a look at the Bayer Black-grass Task Manager at

Big news from harvest this week is that a Lincs grower; Tim lammyman broke the oilseed rape world record with a 6.7 tonne a hectare yielding crop.  This follows on from our harvest news last week where oilseed rape yields are in general doing a little bit better this year and have picked up possibly due to the bright cooler weather earlier in the year.  For the wheat harvest in the south and east a lot of progress has been made and some good yields are reported in excess of 10 tonnes a hectare.  The long dry weekend was a real boost to everyone and lots of progress has been made across the country

That’s all for this week, next week we’ll be discussing options for pre-emergence herbicides.  Until then goodbye.





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