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The extreme weather conditions of last autumn and this spring have undoubtedly impacted soil structure and have left many farmers questioning how to manage their autumn 2020 drilling and cultivations and the impact their decisions will have on grass-weed control.

Ben Coombs, campaign manager for cereal herbicides, catches up with weed biology and management specialist John Cussans from NIAB and independent advisor on soils and cultivations, Philip Wright to discuss what farmers can do to best prepare for the coming season.

Ben - This is Ben Coombs I’m campaign manager for cereal herbicides and I work for Bayer.

John - I'm John Cussans and I'm a weed biology and management specialist at NIAB.

Philip - Hi there I’m Philip Wright, independent advisor on soils and cultivations.

Ben - Hi John and Philip, welcome to this recording of the podcast/some audio for Bayer. I think we’re kind of coming to the end or end is in sight of a very unusual season. I think I'm right in saying it's been just about the wettest autumn and winter on record, followed immediately by the driest spring. So I guess the first place to start is given that we're thinking about weed control, what has been the effect of this really wet autumn winter and really dry spring on weed control this season from your perspective?

John - Ok, so I'll have a go answering that. I think the reality is it's just a year where reflecting how really difficult decision making has been on farm - every single field and sometimes different parts within the field are in a different situation right now. We've got a combination of did people drill early or did they get drilled at all? Maybe they drilled a crop in the autumn under really difficult conditions and it lacked the vigour that it normally would and then overlaid on that, you've got a range of people who applied pre-emergence herbicides early to early drilled crops and didn't get good results because the conditions were so difficult. People who drilled crops but were then unable to spray them at the timing that they would want to, people who drilled crops and perhaps because they were worried about crop effects either reduced or removed elements of their pre-emergence herbicide programme. So, every different combination of all those factors seems to be at play. Incredibly variable picture out there. It's always the case to some extent that black-grass in particular is really bad in places and other people feel that they've done very well this year. And I think this year is more so than previous years in terms of that really mixed picture. And then of course we fell through that, stumbled out of the autumn, into the spring and then you got a whole range of challenging decision making in the spring. When were your opportunities to drill? Were you forced into a spring crop and perhaps you hadn't set out the conditions in the field to drill one? And then what did you do in terms of grass weed management in that spring crop?

Ben - And so then I think Philip from your perspective if John’s focused on maybe what’s above the ground in terms of weed, what's your perspective of what's going to have happened below the ground with soil structure? And what will be the effects on soil structure of the season we've just had?

Philip – That’s a good question, Ben. I think we've gone into this particular autumn winter and now into spring as an extreme wet followed by dry, but an extreme wet the previous year, we were basically the other way around and we were extreme in the dry sense. So, any system that a farm has been operating has been tested to both extremes and it certainly showed the strengths and weaknesses of such systems. And I think it's tested a lot of farmers’ resolve to be able to be flexible and adapt according to the conditions. We had a situation this spring now where possibly we farmers were faced with the question, do I loosen the ground and throw everything nearly away that I’ve tried to prepare in terms of seedbeds to minimally disturb, do I then go and pull all that up and throw that part of it away just to get a crop drilled? And even then, where farmers possibly chose to wait that bit longer, they might have actually found that far better. A number rang me up, a great number rang me up and said, well, do you think I should pull the ground up or should I leave it and go in? And I think for me, the answer was, have you tried to drill? You know, have you tried it yet? And don't bother to put seed in, just go and put it in a corner of the field, an area that you would say, reasonably representative and see how it goes. And a good 50 to 60 percent didn't ring back after that straight away and in the end, they rang back and said, well, it didn't actually work too bad and I put the seed in and carried on drilling and I'm pleased I did. And in hindsight, they were very pleased they did, some of them that lifted the ground and let it dry out, then we didn't get any more rain - so that was equally a challenge for the establishing crop. But for me, I think in all cases the soils that were in better condition structurally and certainly soils that were in better condition from a resilience point of view and an organic matter point of view, those slightly higher on that scale tended to be somewhat easier, somewhat more forgiving. And I think of that season two years ago that was extremely dry and put some serious cracks in those soils, set the soil up for taking those extreme wet periods, weeks and months of last autumn and winter. I think if we hadn't had that previous year, we would probably not be in such a good position.

Ben - I think it kind of then draws into thinking about if we then draw that line John was talking about, and draw the line under this season, it's maybe some have been saved by some good structuring previously. But undoubtedly this season as 

you said, has thrown some challenges at soils and crops. Harvest is just around the corner, it's not too long until the combines will begin rolling. What sort of planning, what sort of thought process should be going through farmers minds at the moment for autumn 20, so the coming drilling window and any cultivations before that now?

Philip - Well, I think if I carry on the theme I was just on and then let John come in on the on sort of husbandry side as well. But certainly, from my point of view, it would be good practice to make sure the kits settled up ready to go. If you're chopping and spreading and returning residues, make sure that everything's right on that score, that you've got a good set of blades, that they're well set, well adjusted, so that we start off right. I think in terms of good practice as well, make sure that your tyre pressures are appropriate, safely minimal, let's call it that (I appreciate that there are some compromises). And I think then get the spade out now and use the roots that are there as your indicator really - they’re going to tell you have they got down efficiently? Are there layers that are wetter? Are there layers where roots have been held up? If that's the case that should flag up as a concern at the moment. And although we've still got to be mindful, we've got some weather to go before now and harvest and we can we can start to make a plan. Certainly, we can start to put ticks in fields boxes that are looking ok. Focus the mind, you know, go for a start into a good area on each field. That will give you a benchmark and a feel for it and then go into, let's say, visibly more challenged areas in terms of the crop that's growing. Dig down and check what the issues are, it might not be a soil constraint, but if it is, then I'd be very surprised if the problem was that deep to be honest I think you might find the majority of the problems are in the top 10, 15, 20cm max, but probably a lot less than that.

Ben - Thanks and so start doing the mapping out in minds of what’s coming up, where problems might lie. Yeah, absolutely, and John, from your perspective, with thinking about the crop husbandry, I guess drilling dates, those sorts of decisions for this autumn, what would your perspective be going ahead into autumn 2020?

John - I mean, I guess there's an element of, as Philip says, just map out where your weed problems are right now and use that in planning for next season. I mean I'd say in terms of grass weed management, fundamentally, you always have two choices. If you've had a significant number of grass weeds in a crop, it's always been the case you've had two choices and one is to deal with the seeds now and prevent seed return through crop destruction or hand weeding, rouging or whatever. Or it is to allow those seeds to shed to harvest the crop and deal with them in the next crop. And, you know, different people depending on where they are in their cropping and perhaps the crop is more valuable now than perhaps it might have been in different seasons because of the rarity of good winter wheat crops, for example, in some areas. We may see less crop destruction going on. But that does mean we really need to focus on managing the weed seeds in the next season. And part of that is going to be I mean, I know a lot of people have talked about there being a bit of a bounce, a rush to drill crops next year because of what a really difficult campaign it was last autumn. I'm not sure there are that many people who've got significant black-grass problems who are actually going to do that to be honest. I think it's so embedded in the psyche now that trying to drill cereal crops in in the first half of September, in the middle of September, when you know that you're under a lot of pressure from grass weeds and you won't get the control that you want to from the pre-ems and you have a very large population in the crop. I think that knowledge is so embedded now that I'm not sure we will perhaps see that enormous bounce that there'll be a great rush to drill. So optimum drilling dates bear that in mind, obviously mapping out where the problem will give you a hierarchy of what fields are going to be most problematic, where you've got least leeway next year.

Ben - Yeah, I guess the principle is that the fundamentals haven't changed in that delaying drilling is a positive for black-grass and it brings with it other challenges as last autumn really highlighted. But, with getting crop drilled its important consideration to consider. Drilling earlier gives more surety of getting crop in the ground, of course, but it brings with it the likelihood of a additional black-grass and so that's a consideration that needs to be thrown into the mix.

John - I think that's where your monitoring of where the problems are this year comes in, that you can have more leeway in some fields than you've got in other fields. But I think growers with significant levels of black-grass will be all too aware that there are some scenarios where if they try and drill an early drilled cereal crop next year, they just will not get a crop. I'm not sure there will be a universal rebound, but yes, it's really focused our minds on how challenging it is to use delayed drilling as a key plank in black-grass management and gets us to focus on some of the other areas I suppose.

Ben - I think then just focusing in on the window that will be there after harvest and before drilling in autumn 20. Philip, would really appreciate your comments on, because it strikes me that there's possibly going to be more to focus on in that window than there has been in recent years because of the effects of this season and the results of that monitoring that you’d recommend farmers are doing around now. What would your advice be on prioritising tasks during the post-harvest window (post-harvest/pre-drilling) for getting soils into a fit state, are there some key tasks that really need to be achieved quickly and first? And how would you structure that window of getting the operations done that need doing?

Philip - We have to start really with part of what we've already discussed, that if we can make the harvest operations as efficient as possible (there are a lot of variables it depends on here), but for example, are you removing straw or are you going to keep straw there? But clearly if straw has been removed, if there's an option to put back FYM or put something else into the mix there, then keeping structure damage, keeping damage to a minimum anyway -  all of this is going to reduce the hassle and the onerous task to come. So again, I think whatever we can do to control where we traffic on the field, to keep that to known areas to bare minimum, then within limits of what we're doing ahead of establishing the next crop then that's the most important starting point prevention rather than cure. And then really it's prioritising which fields, almost working backwards from the answer. With John's points, he's made quite rightly on delaying drilling and knowing the fields that we've got to focus on, then you can start to work backwards from that answer to know what time you've got and then what you've got to do. 

Clearly, making a stale seedbed is an option if we're going to make a stale seedbed to try and stimulate some grass weeds. We in an ideal world need a low dormancy situation, I think keeping as shallow as we can possibly go within limits of good stale seedbed again keeps the powder dry, going any deeper than necessary is never good anyway. I think if we're going to do any form of soil movement ahead of drilling, then the amount of disturbance that we want to put in wants to be a greater level of disturbance earlier on so that when we do eventually drill, we are putting less disturbance in at that point with the commercial crop during operation, for example. We're putting less disturbance in there so if we're going to give some stimulation to black-grass to grow, we want to be doing it sooner and to a greater level than when we actually drill and that would also apply to spring drills as well. And again, I think if you can work to preparing your final seedbed, particularly with minimum disturbance, if you're going to work to preparing your final seedbed as part of the early process of the stale seedbed pass, if you leave it in a sensible state level enough right enough to drill, then you give yourself more options going forward. You're not sort of back end loading the actions that you're doing to create the optimum condition for establishing a commercial crop. As John said, quite rightly, the competitiveness of that crop is vital. So it's ultimately the aim has got to be do the stuff that's right for that following crop, if at the same time we can then do what's necessary to stimulate the black-grass, at the same time, acknowledge that we're trying to manage the soil from a point of view of slug and pest control, giving a shallow amount of tillage can help slug control, clearly depending on what was the previous crop, so there's all those sort of aspects can come in. But probably the overriding factor is having determined what repair is needed, if any at all, then achieve that with as little possible disturbances, we can and certainly aim to tail that disturbance off the nearer we get to drilling that next crop, the commercial crop.

Ben - Thank you. That's really good important lessons. To confuse that or maybe to add another angle into it, John one question that I think is probably worth throwing into the mix here is, is that black-grass itself is sensitive to cultivation the schools of thought depending on - is it best to actually leave the black-grass on the surface or should it be cultivated immediately after harvest? What would your view be and what are the thinking points for the question of is it right to be cultivating immediately after harvest?

John - I mean, I think the reality is there’s not one answer to the question. I mean, my favourite throwaway line when I talk about black-grass is if a farmer wants to know whether they’ve got a good agronomist - ask them what cultivations they should be doing and when? And if they give them an answer, you need to sack the agronomist and get another one because it depends. The answer is it depends. And particularly with this issue of what time should you try and leave grass weed seeds and black-grass seeds on a soil surface and let them suffer mortality because of the difficult conditions that there are on that surface, particularly if you're obviously taking all the crop residues away and leaving them uncovered. Or should you just get straight in after harvest and try and work the surface of the soil to try and stimulate them to germinate? And the answer genuinely is it depends. And we've seen in analysis of old data and specific trials, we wanted to look at this question. You get diametrically opposed answers depending on the season. So, if you have dry conditions through harvest and after harvest, so you've got these dry, harsh conditions on the soil surface.

Two things, first of all, your grass seeds, which are not really designed to be persistent in those sorts of conditions will suffer high levels of direct mortality and whatever cultivations you would want to do probably wouldn't work very well anyway. In that scenario I would say you leave well alone, you're not going to do a very good job of whatever cultivation you want to do. And the weed seeds are sitting on that really dry, parched surface, lots of high levels of UV, maybe some are wetting up and drying and you'll get a lot of mortality. On the other hand, if you've got conditions that we do sometimes get in the summer in the UK where that month is wet, difficult harvest, perhaps and seeds could survive perfectly well on the surface of the soil after harvest there’s plenty of moisture, then by all means cultivate and try and get as much to germinate as possible. And I think that the answer really has got to be to a lot of these questions, and Philip alluded to it as well, what cultivations should I do and when? And the answer is it depends. The answer is always it depends. We know that we've got different conditions post-drilling and wet and dry and people really have got to use those fundamental pieces of knowledge and make their own decisions or advisers have to go through that process for themselves.

Ben - Yeah, I think one of the themes actually, I think Phillip used the phrase of think with the end in mind and think of the result that you have, and that applies to the cultivations and structuring the soil in a physical sense and the interaction of the soil with black-grass in the biological sense. I think that's actually probably one of the really good messages to take out for all of this when looking ahead to the next growing season is think about that result in mind, do some prioritisation and then work through plans of action depending on each individual seed the field’s needs. So really important lessons on that side.

John - Another kind of principle that Philip said and I think is worth bringing out, is that we want to form the seed bed, which is going to form the surface of the growing crop as soon as possible and let it evolve and let whatever weed seeds are readily germinable germinate and be killed off without pre-drilling glyphosate and do that. And that's as true for spring crops as it is for winter crops. You want to make that surface and let it evolve naturally rather than kind of forcing it and cultivating making one surface and then just before you drill you mix it all in and make another surface which is going to be the one that's in the growing crop.

Ben - Philip I wondered if you had any comments to make on how cover crops could be used to help with some of the soil issues which may be present in places following last autumn?

Philip - Yeah Ben I've said I think speaking really as a poacher turned gamekeeper here, I've spent 28 years of my life designing machinery to rip soils to bits so I'm probably very well qualified to talk about this. But I think for me, metal really is a means to an end and you rightly bring the subject up off of cover crops and using basically roots to grow through the soil at all times because at the end of the day roots and growing in the soil, biological and natural activity is the stuff that will actually give you good structure. And whilst metal can be used to help that, it is very much a means to an end and that's really the way I look at it these days. It’s judging how roots are doing it for you and do they need help to be simplistic. And I think ahead of a spring crop, the more I look, the more I learn, at the end of the day don't ever leave soil fallow and bare if you can possibly avoid it. Always try and have something growing in there and as a result of that then, that growing crop can help draw the moisture out as inevitably things went up and as I'm sure everyone's aware of and certainly I know you're aware of, if you look at a field surface as it evolves through a growing season - the weather creates you in the end, a lovely little surface tilt normally. Ok, you get extremes in that extreme weather and water can start to destabilise the surface but the more fibres, the more natural resilience you build into that soil surface the better it gets. And so that weathering action, that wetting and drying action on any soil other than a pure sand will generally create you as a shrinking and swelling action locally on the surface, it will start to create you little fine aggregates. And if you've got more stabilising through roots and biological activity, you get better binders that are exuded that are there that help to hold those little aggregates and keep them into water stable soil you eventually develop tilt basically and then we can use that tilt to drill into without so much work and much effort and the whole thing relies on growing something.

Ben - I think one final area to touch on and it really picks up on a lot of the themes that you've just spoken about their Philip. But I'll go to John first, because this is something that we've discussed before. And it's the idea that actually one of the key features of a cover crop as Philip has sort of alluded to there is to prepare the ground for the next crop, for the spring barley, maybe for the spring cereal. I'm going to play devil’s advocate on this occasion because we were actually in a project we're working on together with some partner farmers and the Black-grass Task Force In Action ran an approach where we looked at using cover crops in a field in Huntingdon, doing a trial in one area of the field without a cover crop and one with and actually in this case, while the soil appeared to be in better condition for drilling at the time of drilling in the cover crop area it looks like the cover crop drilled spring barley has fared a bit worse. So are there any kind of comments that you'd make on why that might be the case and how that might need to evolve and things that are idiosyncratic perhaps to last season that might explain that?

John - I think an honest analysis of what we've done at the farm that's in the Black-grass Task Force would be that we've seen some of the Benefits in terms of soil structure. We've also, to some extent, seen some of the worst risks of growing a cover crop in terms of the crop that follows it itself. And what's been really interesting from my point of view is a real willingness of the grower there to build on those positives, but not throw the baby out with the bathwater. And I think what we saw in fact is a cover crop that although it did struggle in the autumn, actually got going and in the end we got quite a lot of above ground biomass through the winter and into the spring, and it wasn't sprayed off until a few weeks before the crop itself was drilled, which left a lot of that biomass for the drill to have to cope with. Some of the elements of the mix there I think were probably with hindsight if, given that the lack of gap between spraying often and drilling the crop perhaps could have been different. But nevertheless, despite the fact that we've had because of this interference of this large biomass with the drill operation, the effect that we've had on the spring barley that's followed, you can really see the Benefit there has been to the soil structure that underlies it. And I think there's an opportunity there, as I say, to capture those positives and to avoid the negatives. And I think in terms of avoiding the negatives, well, there are two lessons in practice for that particular grower. The first of which I think is just simply to destroy the cover crop a bit earlier, it's enormously tempting to see all that green biomass and think, well, it must be doing a fantastic job why on earth would I want to spray it off around Christmas, early in the new year and “lose it all”. But experience has been that even with cover crops from an autumn sown crop in front of a spring sown crop, even with cover crops which is destroyed pre-Christmas around Christmas and early in the new year you still see those Benefits without the challenge of having to drill. And I think the other lesson is to perhaps take the oat component of the cover crop mix out and replace it with something that might play a slightly different role, because my feeling was that it was that element which was being particularly problematic in terms of the drilling.

Ben - I think that's really, really informative. Thank you both really, really interesting. I hope everyone listening found that very interesting. So I’ll draw it to a close, thank you for your comments, we really appreciate it. And I totally agree, here's to a successful and maybe more simple autumn 2020 drilling and 2020/2021 season. Thank you.

John - Thank you.

Philip – You are more than welcome. Thank you.

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