Read the transcript of the podcast below.
Dr. Black Grass: This is episode three of Dr Blackgrass On Air. The topic today is black grass maps, particularly what useful information aerial maps can tell us. In recent years there's been an explosion in the use of unmanned aerial vehicles in agriculture. Some of these are used for things like nutrient and moisture monitoring or simply aerial photography. Weed mapping with aerial systems has proved to be quite difficult because it's hard to differentiate the colour of weeds from the colour of crops, particularly at a stage in the season when there's still time to do something about it. However, developments in cameras, software, and sensors mean that weed mapping is now a real possibility. Sam Harvey of Bayer outlines some of the developments and capabilities of the technology at the moment.
Sam Harvey: Over the course of the last three years, we've been looking to better understand the population dynamics of black grass within the field using aerial photography so that we can better understand where we need to take a proactive approach in terms of crop destruction to prevent seed return, or manage seed return, and integrate cultural practices such as increased seed rates for the season ahead.
Dr. Black Grass: What technology have you been using to map black grass in the fields?
Sam Harvey: Over the last three years we've used various different approaches to aerial map using fixed-wing drones to capture the differences in the colouration of the black grass in latter stages of heading with the black grass we get that differentiation in colour. It would be nice if we can better capture the images at an earlier stage of the crop cycle so that we can make decisions sooner within the crop. Last year, we looked at some very early images which proved less successful and going forward we'd like to think we could try and tease out the point at which we can identify, and whether that would allow us, with the type of plant that black grass is, to identify it before heading remains to be seen. As camera technology evolves, hopefully that will become possible at some point.
Dr. Black Grass: What kind of difference does having a map make toward herbicides? I'm not talking about crop destruction herbicides like glyphosate but your pre-emergence Liberator or your post-emergence Atlantis.
Sam Harvey: Essentially the map allows you to tailor the points we've just discussed. I wouldn't necessarily suggest it would allow reduction in some of the key herbicides that you talk about in terms of Liberator and Atlantis. It perhaps allows you to tailor your programmed approach in terms of a more heavily stacked approach in certain circumstances or potentially with a later drilling slot to maximize the benefit you're seeing from that herbicide program.
Dr. Black Grass: Thank you Sam. To test out the potential of this technology to support black grass control, Bayer arranged for over 200 hectares of arable land belonging to the Thurlow estate to be mapped earlier this year. Ursula Agriculture is the company which carried out the mapping. Over the last few years they've been refining their technique and can now produce maps that show the precise location and density of black grass at a range of scales, for the Thurlow Estate the maps show the density in five meter by five meter squares but URSULA have the capability to go to much higher resolution, showing it in squares of a few centimetres only. Such precise information is clearly a real benefit when planning black grass control. Andrew Crossley, farm manager at Thurlow and founder of RTK farming, told us about how he plans to use the maps.
Good afternoon, Andrew. You work for RTK Farming and also manage the Thurlow estate. Could you give us a little bit of background about both of these organizations?
Andrew Crossley: Yeah. RTK Farming is a network of fixed base stations and repeaters that covers the eastern region of England from the Thames to the Humber and across past the A1 towards the M1. Thurlow Estate Farms is a block of arable land on the Suffolk / Cambridgeshire / Essex border with combinable crops and a small amount of sugar beet. We farm 5,000 hectares with a rotation of wheat, barley, rape, beans, at the moment.
Dr. Black Grass: Do you have significant black grass problems on this farm?
Andrew Crossley: We're quite lucky that we've had a reasonably diverse rotation for a period of years. Although our black grass population isn't too bad we do have areas which are trickier than others.
Dr. Black Grass: Now, you've recently had some maps done with the aerial photography that Sam has just told us about. What can be seen in these maps that's taken your interest?
Andrew Crossley: What's really interesting in the maps is the different populations of black grass in percentage terms. We can now identify exactly where heavier and lighter infestations are. This saves field walking to identify where they are and it actually quantifies the problem we've got.
The second interesting item is that where we've crop destructed in previous years, we've got lower populations than areas where we didn't crop destruct.
Dr. Black Grass: Did the maps tell you something unexpected or did it really confirm what you knew about the farm already?
Andrew Crossley: I think it confirmed what we thought we knew already but it did show us where there were low populations of black grass that perhaps we hadn't appreciated existed rather than the obvious patches that we see year in, year out.
Dr. Black Grass: How are you going to use the maps to improve your management strategy across the whole farm?
Andrew Crossley: We'll use the maps to target areas of black grass that need more severe control. In other words, focusing on crop destruct in future years. We'll also be able to decide which fields we delay drilling. We found last year that if we delayed drilling for about a month, from late September to late October, there was very, very, very little, if no black grass at all in those delayed drilling fields. Identifying which fields that process should be put into is very important.
Dr. Black Grass: On the map I can see there's some fields that look relatively clean, almost completely clean. What do you put that down to?
Andrew Crossley: I think the fields that are very clean are where we've done a better job of creating a stale seed bed. We've employed drill techniques which don't disturb too much of the soil in that crucial period of drilling after a stale seed bed. We're moving away from a tine drill to a disc drill so that we disturb less of the soil. Usually bad black grass seems to match places of poor drainage on the estate.
Dr. Black Grass: You said you mainly grow cereals on the farm. What is actually in the rotation?
Andrew Crossley: We grow first wheat only. There's one block of barley in the rotation, and then spring crop. We've reduced our winter rape acreage for a number of reasons including the fact that it's quite difficult to control back grass with a reduction in chemistry. We've also introduced a small area each year of forage rye for AD plants because that allows us to have a wider window for a stale seed bed. If there is any black grass grown in the forage rye, which is an extremely competitive crop, we actually remove it from the field before any shedding of seed.
Dr. Black Grass: You have the map for this year, what's your plan for next year? Are you going to map the same area again?
Andrew Crossley: What we'd like to do is we'd like a sequence of maps over a number of years so we can actually see whether the problem is getting worse or better. Anything that quantifies exactly what we're achieving rather than a subjective view of what we're achieving has got to be a useful tactic. We'll also use those maps to be able to identify areas of problems that we weren't aware of from conventional field walking.
Dr. Black Grass: Over what kind of time frame are you going to be continuing to map the farm or look at how you’re making improvements step by step?
Andrew Crossley: I think we'll map the farm every other year. Every year it comes in to first wheat. In terms of time scale for improvement blocks that we've drilled late this year have got no black grass in them. This means that we won't have any seed return from those blocks. If the major problem with black grass is seed return then we've broken the cycle in quite a short period.
Dr. Black Grass: Presumably you're still using quite significant pre-emergence chemistry?
Andrew Crossley: Yeah. We can't let up on our pre-emergence chemistry because we need to use a number of active ingredients. At the moment, our strategy includes Liberator, pendimethalin and Avadex as three crucial products to make sure that we control as much of the black grass at an early stage so that we're not entirely reliant on contact material post-emergence.
Dr. Black Grass: How do you make sure you get the best success with those pre-em products?
Andrew Crossley: The best success, we find, is where we've created an exceptionally good stale seed bed. We've not disturbed the soil too much. We've rolled it to give a good surface to make sure that the active ingredients are evenly applied across the soil surface.
Dr. Black Grass: You mentioned that you use the post-em sparingly. Under what circumstance would you make an application?
Andrew Crossley: We use quite a lot of Atlantis across the farm but we try to use it where other methods of control have not worked in terms of cultural control. If we’ve drilled late and we have no black grass then quite clearly we don't need to use Atlantis - that actually in our minds allows us to then focus the product where it's needed and not where it isn't. It's quite important to us to make sure a product lasts for as long as possible. We'll be very careful about the growth stage of the black grass in terms of when we apply Atlantis. We don't want to apply Atlantis to a black grass plant that's got too big, so timing's crucial to us.
Dr. Black Grass: Finally, what would you say is the big advantage of these maps?
Andrew Crossley: The big advantage to the maps is they show exactly where the black grass is. An agronomist could never, in our minds, walk to the detail that an image shows as to exactly where the problem occurs. They show what level the population is because URSULA have done a fantastic job in showing different black grass densities. I think that's probably the real eye opener as to what a low population looks like in an image and where it exists and where a high population is.
Dr. Black Grass: Thank you, Andrew. For anyone interested in finding out more about the work of the Thurlow Estate, this month’s CPM Magazine is going to have an extensive feature which will develop some of the themes we’ve been talking about today.
Harvest is now in full swing and I’ve managed to catch up with one of our listeners, Jonathan Hodson, to find out how he is getting on. Jonathan farms around 260 hectares east of Hull, and so far he is very pleased with the results. His winter barley yielded very well at over 9 tonnes a hectare and had a specific weight of over 71 kg. These results match well with the picture nationally where the ADAS harvest report says that winter barley yields are above average and the same is true for results from Recommended List trials. Jonathan has also brought in some vining peas and these have also yielded well, his OSR is due to come in this week and he is optimistic it will out do the current farm average of 4.4 tonnes a hectare and once again the picture nationally would support his optimism. I spoke to Richard Ellsden of United Oilseeds and he gave me a quick outline of the picture nationally. He seems to think that about a quarter of the harvest is completed up to around the midlands and so far average yields are 3.7 to 4.1 tonnes a hectare. He didn’t have any information about quality but hopes that over the next week or two we’ll have a better idea about that as well. If you have anything to tell us about how harvest is progressing on your farm please tweet us @Drblackgrass.
That's all we’ve got time for this week. Next week on Dr black grass on air we're going to be talking about using cultivations and glyphosate to kill off blackgrass in preparation for drilling and pre-emergence herbicides until then, goodbye.