Article taken from Farmers Guide, August 2017, written by Dominic Kilburn.
Agrovista technical manager Mark Hemmant is in no doubt - controlling black-grass with herbicides has become a lottery. It's essential, he stressed, that we look at other ways to reduce black-grass pressure and that starts with cultural control.
Mr Hemmant was talking at the company's heavy land trial site called Project Lamport, near Maidwell in Northamptonshire. The trial, now in its fourth year, consists of 14 different rotational systems and is set within high black-grass populations. In fact, ahead of the project starting and the entire site being ploughed, black-grass plants numbered 2,000/m' - a legacy of the continuous wheat/oilseed rape rotation of the preceding 10 years.
""Although we know spring cropping is one answer to the black-grass problem, no-one has actually provided growers with good information and advice on how to establish spring crops on heavy land;' he stated.
Different systems
""Traditionally in this area of the country and on this type of land, it's been extremely difficult to get good seedbeds in the spring with which to establish successful spring crops;' continued technical manager Stewart Woodhead. ""So this project is all about finding the best ways to enable growers to reliably establish spring crops on heavy land while looking at everything possible to reduce black-grass pressure;' he explained.
According to Mr Woodhead, over the life of the project, the trials have managed to demonstrate that crops such as spring wheat and spring barley can be reliably established on the site, albeit with help from cover crops in the rotation. The combination of spring crop and cover crop has helped to reduce black-grass infestation while also providing soil-enhancing benefits.
However, what has also become clear over the past four years is that attention to detail is key, warned Mr Woodhead. ""While an important focus of the trial is to minimise soil disturbance in order to reduce the amount of germinating black-grass, we have seen that even the wrong tyre pressure on a tractor pulling the drill can stir up the soil and encourage black-grass to germinate in the crop;'he highlighted.
Success
Developing into what is proving to be the most successful rotation at Project Lamport in terms of crop establishment and black-grass control, ""System 3"" has featured four years of autumn established cover crops followed by spring wheat. The latest crop, KWS Willow, was direct drilled for minimal soil disturbance on the 28th March at 500 seeds/m2.
""We com bi-drilled and then rolled our cover crop in early September following a pass with an X-Press disc harrow, and the idea with the cover crop is that it remains open enough to 'trick' the black-grass into germinating with it, as it would in a conventional crop," said Mr Woodhead. ""The important thing is that we are not smothering the black-grass to prevent it coming through," he added.
The cover crop was then burnt off with glyphosate in February, some four to six weeks ahead of drilling, followed by a second glyphosate close to drilling in March to kill off any remaining black-grass.
""The cover crop has taken moisture out of the soil as well as 'accidentally' bringing out the black-grass to enable it to be sprayed off and to give us very good control," he commented.
""This is the only plot on the site with more than 98 per cent control of black-grass and, compared with some on the other plots where we have returned as much as 250 blackgrass seeds/m2, with this system we're only putting back 40kg of black-grass seed/ha.""
Mr Hemmant added that when direct drilling into heavy soils like this, 40-60 per cent crop establishment was typical and so it was critical that high seed rates should be considered to ensure the crop is sufficiently competitive against black-grass.
""This particular rotation is working for the farmer. Yes, it's a lot of money to grow and then spray off a cover crop, but what's the alternative?""
Early destruction
In a separate rotational plot where a cover crop was again followed by spring wheat, similarly good results in terms of black-grass control were achieved, but an earlier destruction of the cover crop - in December rather than February- has resulted in improved yields (an additional 0.St/ ha in 2015 and 0.7t/ha in 2016). ""We think the roots of the cover crop held the soil structure together and allowed the direct drilling to take place earlier. Once established the spring wheat was better able to cover the ground because of the earlier destruction of the cover crop," pointed out Mr Hemmant.
Standard practice
If growers on heavy land with traditional wheat/OSR rotations and increasing problems with black-grass ever needed reminding that they are going to have to do something different if they want to remain in business, then the aptly named 'Standard Practice' rotational plot is a demonstration of the stark reality some are facing, suggested Agrovista.
""The initial plough was followed by a first wheat (and full herbicide programme) and gave quite good black-grass control," said Mr Woodhead. ""But three more years including a second wheat followed by OSR and then wheat again, brought all the black-grass back again - just four years after using the plough as the re-set button.
This year we've spent around £150/ ha on black-grass chemistry, we've got 500 black-grass heads/m2 and I expect yields to be in the 5-7t/ha range.""
Mark Hemmant added: ""The question for anyone in this situation is what are they going to do now? Ploughing is not an option as we got 300 black-grass seeds/m2 two years after the plough and we can't herbicide our way out of it. By the second year we'd already lost the benefit of the plough.
""The cost of cover crop seed is in excess of £40/ha but what is there to lose when you are spending £80-150/ ha in herbicide cost and still getting black-grass?""
Strong tap root
Along similar 'Stand Practice' lines, a late sown wheat was drilled after the plough in 2014, followed by Hyvido winter barley in 2015, winter OSR plus a companion plant (berseem clover) in 2016 and this year back to a first wheat (Lili drilled on the 28th October at 450 seeds/m2) following a catch crop of black oat and berseem clover.
""The berseem clover dies with the first frost but it has a strong tap root to push down through the soil and this helped the OSR to establish," explained Mr Woodhead. ""However the catch crop was more there to take up the moisture before the late drilled wheat as it can get difficult to drill wheat after the first week in October in this area.""
According to Mr Woodhead, half as much black-grass was found coming up through the first wheat compared with the other Standard Practice plot, both because of the competitive nature of the Hyvido barley and the late drilled wheat beforehand, he suggested.
""We need 98 per cent control to keep levels of black-grass static. With this system we've had a full herbicide programme and several cultural controls including ploughing and late drilling, and we've used glyphosate, but after four years we are in trouble again, returning more black-grass to the seedbank than we are removing.""
Cover crops and barley
The importance of managing cover crops in tandem with spring barley in the rotation was also in evidence on the trials site. A late sown cover crop was grown in autumn 2014 ahead of a first wheat in 2015 which yielded well, pointed out Mr Woodhead.
For 2016 a cover crop preceded spring barley (KWS Irina at 450 seeds/ m2) which was drilled in late March.
""We drilled the high rate so as not to give any black-grass a chance although care has to be taken as too high a seed rate can result in the crop falling over.
""We want a competitive barley crop but stiffness and brackling resistance should be considered, and so variety choice is important.""
According to Mr Woodhead, the cover crop was destroyed on the 6th December 2016 and sprayed again on the 16th March 2017, with a good result in terms of black-grass. But he said there was more in evidence than he'd have liked, and certainly more than in the successful ""System 3"" which featured spring wheat and cover crops.
""Part of the trouble was because the cover crop was drilled on the 25th August, volunteer barley swamped it so that black-grass which should have come up in the autumn couldn't, and came up later in the crop.
""But we learn from our mistakes," he added.
No herbicide
Another plot was set up to mimic ""System 3"" (cover crop in the autumn followed by spring wheat) but this time with no residual herbicide and the addition of berseem clover with the spring wheat to help further suppress black-grass.
""This didn't work," said Mr Woodhead. ""We'd let the black-grass in by not including the residual herbicide. Rather than try and be clever by drilling a cover crop with the spring wheat, we would have done better to have focused on black-grass control from the start with herbicide.""
Another so-called 're-start' plot highlighted that two direct drilled spring break crops, following cover crops, resulted in two years of reducing black-grass populations. However, in the third year a cultivated crop of first wheat resulted in a ""massive"" return of black-grass.
""Despite using the plough as a re-start with this rotation, two years of cover and spring crops is not necessarily the answer even after the plough. If you are starting with a low level of black-grass then maybe two years of break crops and then a return to wheat is OK, but not if you are starting with high pressure," advised MrWoodhead.
""For this season we reverted to a cover crop followed by spring wheat but it was still unviable and we had to spray the crop off. In this instance we can't plough as it is too soon after the last time and will bring viable black-grass seed to the surface, and so it will have to have perhaps two years of no crops to retrieve the situation.
""All that good work earlier in the rotation has been undone but it shows that farmers will have to be more reactive to the problems they face each season and be prepared to change what they are doing," added Mr Woodhead.
A real benefit
""Cover crops are helping to change the soil moisture level and structure of heavy land ahead of drilling spring cereals, and they can bring a benefit to both crop yield and black-grass control," summed up Mr Hemmant.
""It's important that they don't smother the ground, and that they remain open enough to allow blackgrass to germinate within them," he reminded.
""However, we are showing here that although cover crops and spring break crops are working, it also demonstrates how quickly you can go from a good position to a bad one.
""When we are in a muddle it can take a big effort to get it back again!
""That said, two of the rotations we are operating here are growing profitable crops and because there has been a massive switch to spring cropping in the UK, we are trying to help those on similarly heavy land sites like this.
""The big gain too is for those who aren't in a muddle yet. We hope we can show them something to learn from, and which offers a prompt for them to change," he added.