Article taken from the Farm Contractor & Large Scale Farmer, written by John Swire
The meeting started off with an introduction by Dave Gardner of the RASE. MR Gardner stated that the wheat/oilseed rape system of farming which has underpinned British arable production for the last 30 years was broken due to the joint issues of soil organic matter and the continuing threat of blackgrass. Further, he maintained that the days of producing a budget from nine tonnes of wheat and four tonnes of oilseed rape per hectare were long gone. The problem is that if we carry on this way, the crops will eventually be choked out by the weed and so we have got to look at some radical solutions.
Dr Stephen Moss, formerly of Rothamstead, told the audience that an understanding of the agri-ecology of blackgrass has underpinned the whole approach to the non chemical control of weeds. “Blackgrass is an annual weed propagated solely by seeds, so for long term control seed must be minimised. The one weak point of the plant is that as a rule only 3% of the seeds will survive three years burial, which is relatively rapid although it begins from a very high starting point. Most seed are shed in June and July before harvest. A population of 12 blackgrass plants per m/sq will result in an average 5% yield loss. Os the aim is to get down to below 5% yield loss. So the aim is to get down to below 5 plants per m/sq.
“Around 80% of the blackgrass will emerge in the autumn followed by a smaller peak in the spring. The emergence of the oilseed rape crop over the last 40 years and the trend to plant winter wheat earlier and earlier means that with these emergence patterns, the blackgrass coming up in the crop makes it more and more difficult to control. With the continuing problems with herbicide resistance you cannot rely on herbicides to control the problem. So the reason blackgrass has become an issue is down to its agriecology.
As a result, farmers and growers need to look at a whole combination of measures to control blackgrass. Dr Moss sees the five main aspects of non chemical control, rotations, ploughing, delayed autumn drilling, spring cropping and fallowing, or grass ley breaks. As already stated, the prevalence of autumn sown crops is one of the main reasons why blackgrass is a problem in the UK. “More balanced rotations are needed on many farms, not just for blackgrass control but also to reduce the impact of pest and diseases and improve soil fertility. It is difficult to quantify the direct benefits of rotations on blackgrass control, although the inclusion of spring sown crops in any rotation will be beneficial. There is no simple blueprint for a perfect rotation they must be developed at individual farm levels.
“Ploughing reduces the risk fgrom grass weeds by burying freshly shed seeds to a depth of below 5cms from which seedlings are unlikely. Because blackgrass seeds are relatively non persistent in the seed bank, fewer older buried seeds are brought back up to the surface, especially if ploughing is done on a rotational basis, once every 3-6 years, for example. Another potential benefit of rotational ploughing is that older, less selected seeds may be brought back to the soil surface, thus increasing the proportion of susceptible plants in the weed population. However it must be remembered that the value of later drilling will vary from year to year. “About 80% of blackgrass emergence occurs in autumn, so spring sown crops tend to be much less affected and have given a consistently good reduction in weed infestation in field trials.” Unfortunately establishing crops in the spring can be difficult, especially on heavy soils and because herbicide choice is more limited. Farmers must choose the most appropriate spring crops for their own farm.
For example, spring barley is more effective than spring wheat but there is a lack of information on the effectiveness of other spring sown crops.
“Fallowing or grass ley breaks are being increasingly considered as a means of reducing blackgrass infestations. A grass ley break of two to three years is also a very good option. It must be noted that seed persistence data and farm experience both support the view that a one year fallow or grass ley is not long enough and farmers should also be aware of solving the blackgrass problem and then introducing a ryegrass problem in subsequent arable crops.”
Cover crops
“Farmers and growers need to find new ways of controlling blackgrass and deliver a profitable crops,” according to Mark Hemmant of Agrovista. “To this end Agrovista has established Project Lamport to look at ways to solve the problem. We believe that spring cropping could well be the way forward with a competitive crop, preferably barley over wheat and we think that the missing piece in the jigsaw would be a cover crop. The cover crop would dry the heavy land out to allow us to plant the spring barley and would dry the heavy land out to allow us to plant the spring barley and would also put some structure into the soil.
“We didn’t want a cover crop that was sown in the autumn and prevents the blackgrass from germination because this means that the seed is still there waiting for an opportunity. So our cover crop will extract the moisture from the heavy soil in the winter and equally as important will not interfere with the following crop yield. This will allow the blackgrass to germinate and produce a lot of biomass and if it is destroyed in February or March does not produce any seed.
The meeting started off with an introduction by Dave Gardner of the RASE. MR Gardner stated that the wheat/oilseed rape system of farming which has underpinned British arable production for the last 30 years was broken due to the joint issues of soil organic matter and the continuing threat of blackgrass. Further, he maintained that the days of producing a budget from nine tonnes of wheat and four tonnes of oilseed rape per hectare were long gone. The problem is that if we carry on this way, the crops will eventually be choked out by the weed and so we have got to look at some radical solutions.
Dr Stephen Moss, formerly of Rothamstead, told the audience that an understanding of the agri-ecology of blackgrass has underpinned the whole approach to the non chemical control of weeds. “Blackgrass is an annual weed propagated solely by seeds, so for long term control seed must be minimised. The one weak point of the plant is that as a rule only 3% of the seeds will survive three years burial, which is relatively rapid although it begins from a very high starting point. Most seed are shed in June and July before harvest. A population of 12 blackgrass plants per m/sq will result in an average 5% yield loss. Os the aim is to get down to below 5% yield loss. So the aim is to get down to below 5 plants per m/sq.
“Around 80% of the blackgrass will emerge in the autumn followed by a smaller peak in the spring. The emergence of the oilseed rape crop over the last 40 years and the trend to plant winter wheat earlier and earlier means that with these emergence patterns, the blackgrass coming up in the crop makes it more and more difficult to control. With the continuing problems with herbicide resistance you cannot rely on herbicides to control the problem. So the reason blackgrass has become an issue is down to its agriecology.
As a result, farmers and growers need to look at a whole combination of measures to control blackgrass. Dr Moss sees the five main aspects of non chemical control, rotations, ploughing, delayed autumn drilling, spring cropping and fallowing, or grass ley breaks. As already stated, the prevalence of autumn sown crops is one of the main reasons why blackgrass is a problem in the UK. “More balanced rotations are needed on many farms, not just for blackgrass control but also to reduce the impact of pest and diseases and improve soil fertility. It is difficult to quantify the direct benefits of rotations on blackgrass control, although the inclusion of spring sown crops in any rotation will be beneficial. There is no simple blueprint for a perfect rotation they must be developed at individual farm levels.
“Ploughing reduces the risk fgrom grass weeds by burying freshly shed seeds to a depth of below 5cms from which seedlings are unlikely. Because blackgrass seeds are relatively non persistent in the seed bank, fewer older buried seeds are brought back up to the surface, especially if ploughing is done on a rotational basis, once every 3-6 years, for example. Another potential benefit of rotational ploughing is that older, less selected seeds may be brought back to the soil surface, thus increasing the proportion of susceptible plants in the weed population. However it must be remembered that the value of later drilling will vary from year to year. “About 80% of blackgrass emergence occurs in autumn, so spring sown crops tend to be much less affected and have given a consistently good reduction in weed infestation in field trials.” Unfortunately establishing crops in the spring can be difficult, especially on heavy soils and because herbicide choice is more limited. Farmers must choose the most appropriate spring crops for their own farm.
For example, spring barley is more effective than spring wheat but there is a lack of information on the effectiveness of other spring sown crops.
“Fallowing or grass ley breaks are being increasingly considered as a means of reducing blackgrass infestations. A grass ley break of two to three years is also a very good option. It must be noted that seed persistence data and farm experience both support the view that a one year fallow or grass ley is not long enough and farmers should also be aware of solving the blackgrass problem and then introducing a ryegrass problem in subsequent arable crops.”
Cover crops
“Farmers and growers need to find new ways of controlling blackgrass and deliver a profitable crops,” according to Mark Hemmant of Agrovista. “To this end Agrovista has established Project Lamport to look at ways to solve the problem. We believe that spring cropping could well be the way forward with a competitive crop, preferably barley over wheat and we think that the missing piece in the jigsaw would be a cover crop. The cover crop would dry the heavy land out to allow us to plant the spring barley and would dry the heavy land out to allow us to plant the spring barley and would also put some structure into the soil.
“We didn’t want a cover crop that was sown in the autumn and prevents the blackgrass from germination because this means that the seed is still there waiting for an opportunity. So our cover crop will extract the moisture from the heavy soil in the winter and equally as important will not interfere with the following crop yield. This will allow the blackgrass to germinate and produce a lot of biomass and if it is destroyed in February or March does not produce any seed.