As IPM (integrated pest management) becomes part of the production landscape for tillage farming, alternative and complementary practices for weed control must come more into focus.
Cultural control will have to feature on most tillage farms for the partial control of normal and difficult weed spectrums.
So, at a recent Lemken ‘Cultivation Seminar’at TFM Comerfords Ltd in Ballycallan, Co Kilkenny, it was interesting to hear that genuine replicated research on cultural weed control has already begun in Britain.
Lemken is a partner in this research, along with British distribution giant Agrii.
But it is interesting to note that this is not driven by the need to be IPM compliant but rather by the much more pressing requirement for actual control, given the number of actives that have failed against blackgrass due to the continuous development of herbicide resistance.
And with far fewer new actives likely to be in the pipeline for the years ahead, the inability to control this huge problem would effectively cause the end of winter wheat production for many British growers.
So, this collaborative research effort is driven more by necessity than any opportunity it may generate. Cultural control is seen as one of the few options to significantly reduce weed pressure in fields and, in so doing, to hopefully improve overall control levels and prolong the effective life of the remaining products in different areas.
It must also be said that these same cultural techniques can be used to help control other weed problems and help minimise the pressure to develop resistance following intensive use of single modes of action.
In parts of Britain, some areas with heavy blackgrass infestation have used up nearly all available chemical herbicide families as resistance continues to evolve in this troublesome weed.
With 100 ears of blackgrass per square metre roughly equivalent to a yield reduction of one tonne per hectare, control is obviously important. And infestation levels of this magnitude would be deemed to be low for some fields.
At the Cultivation Seminar, Lemken general manager Mark Ormond outlined how the combination of cultivation and chemical use was now being trialled in Britain by Agrii.
The objective of the experiment was to reduce the overall pressure on the herbicides by using cultivation options to help reduce the overall weed pressure in the crop.
As Mark Ormond sees it, blackgrass is becoming an increasingly big problem and it has moved further north in Britain in recent years. And he suggested that it is only a matter of time before the problem raises its ugly head in Ireland.
The principle behind the approach is to use some combination of cultivation techniques to help result in fewer plants to kill in the following crop.
While this technically reduces the pressure to produce resistance (because there are fewer plants present to survive a chemical treatment), it may also help to improve the efficiency of the chemical applied because there will be less vegetation in the crop, making it easier to get better control of the grass weeds present. In dense canopies, it is more difficult to get good coverage on all plants.
Cultural help essential
In practical terms, it will require some combination of cultural and chemical control to tame this curse for British growers.
The question is what are the best cultural options to use, as all methods will cost money and so growers need to know the best options to deliver the greatest possible reduction in blackgrass (or any grass) numbers in the field.
It is widely accepted that the tight winter wheat rotation, coupled with early drilling, has helped the severity of the problem and this, in turn, has helped to build resistance.
Previous research on blackgrass had shown that 100 ears/m2 could decrease wheat yield by 1.0 t/ha and that a minimum of 96% control is essential to begin to reduce blackgrass seed numbers being returned to the soil for longer term reduction.
Even good control using chemicals at their maximum efficiency would often not achieve this control level in highly infested crops and, so, additional help is needed in the long term.
Research
This research involved an intricate trial design in a heavily infested field, which had 1,000 blackgrass plants per square metre on the untreated stubble.
In the first year, a combination of ploughing, direct drilling and min-tilling were used as large plots in the field and then these were followed by different rotational combinations of the same cultivation methods (sown at right angles), in conjunction with early and late drilling dates.
Perhaps it was not surprising to find that the plough was by far the most successful cultural control technique in reducing blackgrass pressure in the first year of the experiment.
Figure 1 shows the success of the plough (good ploughing) in reducing the number of plants present on those plots. Early direct drilling resulted in the biggest blackgrass infestation, closely followed by a one-pass shallow tillage establishment. The results in Figure 1 were from year one of the experiment.
The trial was laid out differently the following year to overlay the preceding trial, resulting in some small patches of ploughing after ploughing, min-till after ploughing, ploughing after direct drilling, etc, so rotational cultivation systems were being examined.
Interestingly, the plough after plough was among the worst in year two when the seeds ploughed down in year one were ploughed back up again in the following year to cause a serious infestation problem.
Rotational ploughing
Because of how the trial was designed, it could isolate different combinations and sequences of treatments. It was obvious from the results to date that rotational ploughing offered far better control of this grass weed than the other cultural treatments.
But the frequency of ploughing needed to be a maximum of one in three to maintain the benefit achieved in the first year.
The challenge is to bury the bulk of the seeds deep in the profile and to wait until they lose viability before they are ploughed up again.
In all instances, later drilling helped reduce infestation in that it enabled seeds close to the surface to germinate and grow in a type of stale seedbed.
These were then present in advance of planting and this flush of weeds was burned off using glyphosate prior to drilling. This reduced the number of weed seeds available to germinate at the surface once the crop was sown.
And this later drilling finding helped blackgrass numbers regardless of the cultural treatment used.
It was also of interest that the treatment that had the highest blackgrass infestation was strip direct drilling. Even with this technique, infestations were still reduced when planting was delayed, Mark said.
While these trials are focused at blackgrass, Mark indicated that the methodology involved would apply to most grass weed problems (and also many broad-leaved weeds).
The combination of ploughing and non-inversion using stale seedbeds is a useful and successful cultural weed control method and can be used successfully for many other problems, such as sterile brome.
However, the plough treatment must be about good ploughing with good skimming and trash burial. Failure to achieve total trash burial will negate a big proportion of the potential benefit of ploughing for cultural weed control. The same situation applies to sterile brome control.
The second critical factor is that the ploughed ground not be ploughed again for at least two more seasons and, preferably, three. Leave the buried weed seeds buried. If they grow down there, they may not emerge but there may also be something else going on in the soil that seems to take a level of viability from the buried seeds.
Good ploughing booklet
Lemken produced a booklet on the importance of good ploughing and the principles involved.
Ploughing that only blackens a stubble and makes the field unlevel, is not worthy of the name and provides very little net benefit combined from the high cost.
Good ploughing can be more of a challenge with modern high capacity ploughs, especially those with adjustable furrow width.
A number of speakers on the night emphasised the need for the plough wing to be 3cm to 5cm narrower than the furrow width. This is essential because the uncut soil then acts as a hinge to force the sod to turn over. This is what provides the essential inversion which is also critical to achieve good burial following adequate skimming.
Failure to leave this hinge increases the risk that the sod may just push sideways rather than invert fully.
Cultural control can help reduce weed problems and stale seedbeds can significantly help reduce the weed burden. Rotational ploughing can be a useful technique to help reduce weed pressure over time.Later drilling, particularly following a stale seedbed, helps to decrease grass weed and broadleaved weed pressure in winter crops.
As IPM (integrated pest management) becomes part of the production landscape for tillage farming, alternative and complementary practices for weed control must come more into focus.
Cultural control will have to feature on most tillage farms for the partial control of normal and difficult weed spectrums.
So, at a recent Lemken ‘Cultivation Seminar’at TFM Comerfords Ltd in Ballycallan, Co Kilkenny, it was interesting to hear that genuine replicated research on cultural weed control has already begun in Britain.
Lemken is a partner in this research, along with British distribution giant Agrii.
But it is interesting to note that this is not driven by the need to be IPM compliant but rather by the much more pressing requirement for actual control, given the number of actives that have failed against blackgrass due to the continuous development of herbicide resistance.
And with far fewer new actives likely to be in the pipeline for the years ahead, the inability to control this huge problem would effectively cause the end of winter wheat production for many British growers.
So, this collaborative research effort is driven more by necessity than any opportunity it may generate. Cultural control is seen as one of the few options to significantly reduce weed pressure in fields and, in so doing, to hopefully improve overall control levels and prolong the effective life of the remaining products in different areas.
It must also be said that these same cultural techniques can be used to help control other weed problems and help minimise the pressure to develop resistance following intensive use of single modes of action.
In parts of Britain, some areas with heavy blackgrass infestation have used up nearly all available chemical herbicide families as resistance continues to evolve in this troublesome weed.
With 100 ears of blackgrass per square metre roughly equivalent to a yield reduction of one tonne per hectare, control is obviously important. And infestation levels of this magnitude would be deemed to be low for some fields.
At the Cultivation Seminar, Lemken general manager Mark Ormond outlined how the combination of cultivation and chemical use was now being trialled in Britain by Agrii.
The objective of the experiment was to reduce the overall pressure on the herbicides by using cultivation options to help reduce the overall weed pressure in the crop.
As Mark Ormond sees it, blackgrass is becoming an increasingly big problem and it has moved further north in Britain in recent years. And he suggested that it is only a matter of time before the problem raises its ugly head in Ireland.
The principle behind the approach is to use some combination of cultivation techniques to help result in fewer plants to kill in the following crop.
While this technically reduces the pressure to produce resistance (because there are fewer plants present to survive a chemical treatment), it may also help to improve the efficiency of the chemical applied because there will be less vegetation in the crop, making it easier to get better control of the grass weeds present. In dense canopies, it is more difficult to get good coverage on all plants.
Cultural help essential
In practical terms, it will require some combination of cultural and chemical control to tame this curse for British growers.
The question is what are the best cultural options to use, as all methods will cost money and so growers need to know the best options to deliver the greatest possible reduction in blackgrass (or any grass) numbers in the field.
It is widely accepted that the tight winter wheat rotation, coupled with early drilling, has helped the severity of the problem and this, in turn, has helped to build resistance.
Previous research on blackgrass had shown that 100 ears/m2 could decrease wheat yield by 1.0 t/ha and that a minimum of 96% control is essential to begin to reduce blackgrass seed numbers being returned to the soil for longer term reduction.
Even good control using chemicals at their maximum efficiency would often not achieve this control level in highly infested crops and, so, additional help is needed in the long term.
Research
This research involved an intricate trial design in a heavily infested field, which had 1,000 blackgrass plants per square metre on the untreated stubble.
In the first year, a combination of ploughing, direct drilling and min-tilling were used as large plots in the field and then these were followed by different rotational combinations of the same cultivation methods (sown at right angles), in conjunction with early and late drilling dates.
Perhaps it was not surprising to find that the plough was by far the most successful cultural control technique in reducing blackgrass pressure in the first year of the experiment.
Figure 1 shows the success of the plough (good ploughing) in reducing the number of plants present on those plots. Early direct drilling resulted in the biggest blackgrass infestation, closely followed by a one-pass shallow tillage establishment. The results in Figure 1 were from year one of the experiment.
The trial was laid out differently the following year to overlay the preceding trial, resulting in some small patches of ploughing after ploughing, min-till after ploughing, ploughing after direct drilling, etc, so rotational cultivation systems were being examined.
Interestingly, the plough after plough was among the worst in year two when the seeds ploughed down in year one were ploughed back up again in the following year to cause a serious infestation problem.
Rotational ploughing
Because of how the trial was designed, it could isolate different combinations and sequences of treatments. It was obvious from the results to date that rotational ploughing offered far better control of this grass weed than the other cultural treatments.
But the frequency of ploughing needed to be a maximum of one in three to maintain the benefit achieved in the first year.
The challenge is to bury the bulk of the seeds deep in the profile and to wait until they lose viability before they are ploughed up again.
In all instances, later drilling helped reduce infestation in that it enabled seeds close to the surface to germinate and grow in a type of stale seedbed.
These were then present in advance of planting and this flush of weeds was burned off using glyphosate prior to drilling. This reduced the number of weed seeds available to germinate at the surface once the crop was sown.
And this later drilling finding helped blackgrass numbers regardless of the cultural treatment used.
It was also of interest that the treatment that had the highest blackgrass infestation was strip direct drilling. Even with this technique, infestations were still reduced when planting was delayed, Mark said.
While these trials are focused at blackgrass, Mark indicated that the methodology involved would apply to most grass weed problems (and also many broad-leaved weeds).
The combination of ploughing and non-inversion using stale seedbeds is a useful and successful cultural weed control method and can be used successfully for many other problems, such as sterile brome.
However, the plough treatment must be about good ploughing with good skimming and trash burial. Failure to achieve total trash burial will negate a big proportion of the potential benefit of ploughing for cultural weed control. The same situation applies to sterile brome control.
The second critical factor is that the ploughed ground not be ploughed again for at least two more seasons and, preferably, three. Leave the buried weed seeds buried. If they grow down there, they may not emerge but there may also be something else going on in the soil that seems to take a level of viability from the buried seeds.
Good ploughing booklet
Lemken produced a booklet on the importance of good ploughing and the principles involved.
Ploughing that only blackens a stubble and makes the field unlevel, is not worthy of the name and provides very little net benefit combined from the high cost.
Good ploughing can be more of a challenge with modern high capacity ploughs, especially those with adjustable furrow width.
A number of speakers on the night emphasised the need for the plough wing to be 3cm to 5cm narrower than the furrow width. This is essential because the uncut soil then acts as a hinge to force the sod to turn over. This is what provides the essential inversion which is also critical to achieve good burial following adequate skimming.
Failure to leave this hinge increases the risk that the sod may just push sideways rather than invert fully.
Cultural control can help reduce weed problems and stale seedbeds can significantly help reduce the weed burden. Rotational ploughing can be a useful technique to help reduce weed pressure over time.Later drilling, particularly following a stale seedbed, helps to decrease grass weed and broadleaved weed pressure in winter crops. 
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