Grain farmers’ margins in the UK can go up or down by £1,648, depending on the establishment method and crop choice, where blackgrass is an issue.
Rothamsted Research reports that the weed costs the UK economy £400m, or 1.2bn loaves of bread, each year, so research is vital for the viability of cereal growers.
The finding comes from Agrii’s Stow Longa trial site, which we visited with Lemken. Agrii, a large agronomic advisory service, partners with a number of farmers across the UK to conduct on-farm research and crop trials.
The Stow Longa site in the east of England, where blackgrass has been one of the main research focuses for the past 20 years, hosts many trials, including a crop establishment and rotation trial – which is now in its 10th year.
Steve Corbett, Agrii trials manager, explained that while herbicides are still an important tool in fighting blackgrass, resistance is an issue. He has seen the blackgrass control provided by certain herbicides drop from 90% to 20% within one year. Therefore, cultural control has been recognised as critical in controlling blackgrass.
The main result from the many years of research is that no single control measure will provide the necessary level of control to reduce weed populations.
“Cultural control measures stack up and help keep the numbers of grassweeds as low as possible. Then, when you come in with herbicide, which only works on a certain percentage, it’s a numbers game,” Steve explained.
If you have partial control with a herbicide, but you are starting from a small number of plants, you can still achieve good control if the cultural control measures are in place. If they are not, and numbers are increasing, herbicides alone will not help to bring the issue under control.
Spring crops have lowest levels
The crop establishment and rotation trial is a large-scale trial, which involves six crops across seven establishment systems each year, on 1ha blocks. The crop rotation, establishment systems and crop husbandry practices are not fixed, as they are altered to reflect current on-farm practices. The trial also involves seed drill manufacturers, which means that nearly every popular seed drill has planted crops as part of this trial over the years.
Results from the trial show a strong relationship between the number of blackgrass ears/m2 and the gross margin of that treatment. The treatment with the highest gross margin, spring barley established by ploughing, was the only treatment in 2023 with no blackgrass ears, while the treatment with the lowest margin had the most amount of blackgrass (274 ears/m2).
This trial also shows that spring crops are an effective option to reduce blackgrass numbers. Spring oats and spring barley had the lowest average blackgrass ears/m2 when all cultivation systems are taken into account. This then resulted in the two spring crops being the most profitable crops in the trial last year.
Rotational ploughing a good tool
In addition to this, despite the extra cost of ploughing, the ploughed treatments have produced an average of £218/ha higher margin per year across eight years of trials when compared to minimum tillage and direct drilling, and an extra £112/ha/year when compared to deep tillage.
Despite these results, Steve said that farmers should be flexible in their establishment system. If a field with a high blackgrass population is ploughed, ploughing it again the following year will lead to many of these seeds being brought back up to the surface.
Better results have been seen in the trial site with rotational ploughing, where the blackgrass seeds are ploughed down and minimum tillage or strip tillage techniques are then used for a number of years, so that the blackgrass seeds are not brought back up to the surface.
Steve pointed out that it is a clay loam site, and while there is some drainage, it could be improved. This means that the soil can be quite wet, which blackgrass seems to thrive in. He said that everything that happens on the trial site relates to the soil type, so practices that succeed here may not be as beneficial on a different soil type, and the establishment systems that struggle here, may be more suitable for a different type of soil.
Direct drilling
For example, while direct drilling has proven successful on some of Agrii’s other trial sites, it has been a constant challenge on this heavy, high-silt soil. The trial has shown that hybrid barley works well in a direct drill system due to its vigorous rooting, but continuous no-till over a number of years will likely lead to a build-up of weed pressure.
Steve said that it is trickier to establish crops in a no-till scenario. When blackgrass is present, it is vital to ensure that full establishment is achieved, as blackgrass will grow in any patches in a crop. This issue is more visible when the straw from a previous crop is chopped and incorporated. The trash, especially if not spread evenly, can impede establishment and lead to these patches of blackgrass.
Blackgrass emerging after ploughing.
The trial has also shown that direct drilled beans were more affected by drought. This may seem counter-intuitive, as a non-cultivated soil should conserve more moisture. However, due to the heaviness of the soil, the bean roots were not able to grow through compaction in the soil, so they did not have access to the conserved moisture.
Sub soiling
Most farms would include cover crops as part of their farming system where direct drilling is involved, in part to alleviate this compaction and improve soil structure, but it has been difficult to grow them on this farm due to the soil type. Therefore, a trial was conducted in the 2021/2022 growing season to see if low-disturbance subsoiling could be the answer for direct drilling.
In the crop establishment and rotation trial, half of the winter wheat block was subsoiled post-harvest. Cover crops were also planted in some of the cultivation treatments. The block was then left over winter before planting spring oats.
The subsoiling provided an increase in the spring oats yield in nearly every treatment. In the direct drill treatment, the increase was 1.06t/ha, with a rise of 0.84t/ha in the ploughed plot.
Where cover crops were planted, the increases were less. This may indicate that the cover crops are doing some of the compaction alleviation that the subsoiler does. Across all plots, the average increase in yield was 0.67t/ha. This increases the crop’s profit margin by £85.15 after the subsoiling costs are taken into account.
Steve warned that farmers need to ensure that the soil is in a suitable condition before subsoiling takes place. If the soil is too wet, the subsoiler may cause damage rather than alleviating it by smearing the soil and causing further compaction. He also said that subsoiling does not have to be too deep.
Zero-tolerance
If blackgrass does appear on your farm, Steve advised to take a zero-tolerance approach and to burn off small areas before the weeds head out if rogueing is not possible. He said that farmers must quickly learn about their problem, map them, and examine has worked or not worked on their own farms.
“We were too slow off the mark and didn’t realise the impact it would have on us; it’s all about attention to detail,” he added.
Grain farmers’ margins in the UK can go up or down by £1,648, depending on the establishment method and crop choice, where blackgrass is an issue.
Rothamsted Research reports that the weed costs the UK economy £400m, or 1.2bn loaves of bread, each year, so research is vital for the viability of cereal growers.
The finding comes from Agrii’s Stow Longa trial site, which we visited with Lemken. Agrii, a large agronomic advisory service, partners with a number of farmers across the UK to conduct on-farm research and crop trials.
The Stow Longa site in the east of England, where blackgrass has been one of the main research focuses for the past 20 years, hosts many trials, including a crop establishment and rotation trial – which is now in its 10th year.
Steve Corbett, Agrii trials manager, explained that while herbicides are still an important tool in fighting blackgrass, resistance is an issue. He has seen the blackgrass control provided by certain herbicides drop from 90% to 20% within one year. Therefore, cultural control has been recognised as critical in controlling blackgrass.
The main result from the many years of research is that no single control measure will provide the necessary level of control to reduce weed populations.
“Cultural control measures stack up and help keep the numbers of grassweeds as low as possible. Then, when you come in with herbicide, which only works on a certain percentage, it’s a numbers game,” Steve explained.
If you have partial control with a herbicide, but you are starting from a small number of plants, you can still achieve good control if the cultural control measures are in place. If they are not, and numbers are increasing, herbicides alone will not help to bring the issue under control.
Spring crops have lowest levels
The crop establishment and rotation trial is a large-scale trial, which involves six crops across seven establishment systems each year, on 1ha blocks. The crop rotation, establishment systems and crop husbandry practices are not fixed, as they are altered to reflect current on-farm practices. The trial also involves seed drill manufacturers, which means that nearly every popular seed drill has planted crops as part of this trial over the years.
Results from the trial show a strong relationship between the number of blackgrass ears/m2 and the gross margin of that treatment. The treatment with the highest gross margin, spring barley established by ploughing, was the only treatment in 2023 with no blackgrass ears, while the treatment with the lowest margin had the most amount of blackgrass (274 ears/m2).
This trial also shows that spring crops are an effective option to reduce blackgrass numbers. Spring oats and spring barley had the lowest average blackgrass ears/m2 when all cultivation systems are taken into account. This then resulted in the two spring crops being the most profitable crops in the trial last year.
Rotational ploughing a good tool
In addition to this, despite the extra cost of ploughing, the ploughed treatments have produced an average of £218/ha higher margin per year across eight years of trials when compared to minimum tillage and direct drilling, and an extra £112/ha/year when compared to deep tillage.
Despite these results, Steve said that farmers should be flexible in their establishment system. If a field with a high blackgrass population is ploughed, ploughing it again the following year will lead to many of these seeds being brought back up to the surface.
Better results have been seen in the trial site with rotational ploughing, where the blackgrass seeds are ploughed down and minimum tillage or strip tillage techniques are then used for a number of years, so that the blackgrass seeds are not brought back up to the surface.
Steve pointed out that it is a clay loam site, and while there is some drainage, it could be improved. This means that the soil can be quite wet, which blackgrass seems to thrive in. He said that everything that happens on the trial site relates to the soil type, so practices that succeed here may not be as beneficial on a different soil type, and the establishment systems that struggle here, may be more suitable for a different type of soil.
Direct drilling
For example, while direct drilling has proven successful on some of Agrii’s other trial sites, it has been a constant challenge on this heavy, high-silt soil. The trial has shown that hybrid barley works well in a direct drill system due to its vigorous rooting, but continuous no-till over a number of years will likely lead to a build-up of weed pressure.
Steve said that it is trickier to establish crops in a no-till scenario. When blackgrass is present, it is vital to ensure that full establishment is achieved, as blackgrass will grow in any patches in a crop. This issue is more visible when the straw from a previous crop is chopped and incorporated. The trash, especially if not spread evenly, can impede establishment and lead to these patches of blackgrass.
Blackgrass emerging after ploughing.
The trial has also shown that direct drilled beans were more affected by drought. This may seem counter-intuitive, as a non-cultivated soil should conserve more moisture. However, due to the heaviness of the soil, the bean roots were not able to grow through compaction in the soil, so they did not have access to the conserved moisture.
Sub soiling
Most farms would include cover crops as part of their farming system where direct drilling is involved, in part to alleviate this compaction and improve soil structure, but it has been difficult to grow them on this farm due to the soil type. Therefore, a trial was conducted in the 2021/2022 growing season to see if low-disturbance subsoiling could be the answer for direct drilling.
In the crop establishment and rotation trial, half of the winter wheat block was subsoiled post-harvest. Cover crops were also planted in some of the cultivation treatments. The block was then left over winter before planting spring oats.
The subsoiling provided an increase in the spring oats yield in nearly every treatment. In the direct drill treatment, the increase was 1.06t/ha, with a rise of 0.84t/ha in the ploughed plot.
Where cover crops were planted, the increases were less. This may indicate that the cover crops are doing some of the compaction alleviation that the subsoiler does. Across all plots, the average increase in yield was 0.67t/ha. This increases the crop’s profit margin by £85.15 after the subsoiling costs are taken into account.
Steve warned that farmers need to ensure that the soil is in a suitable condition before subsoiling takes place. If the soil is too wet, the subsoiler may cause damage rather than alleviating it by smearing the soil and causing further compaction. He also said that subsoiling does not have to be too deep.
Zero-tolerance
If blackgrass does appear on your farm, Steve advised to take a zero-tolerance approach and to burn off small areas before the weeds head out if rogueing is not possible. He said that farmers must quickly learn about their problem, map them, and examine has worked or not worked on their own farms.
“We were too slow off the mark and didn’t realise the impact it would have on us; it’s all about attention to detail,” he added.
SHARING OPTIONS