Crowds of over 400 growers and members of the industry descended on Kilkenny last week for this year’s Teagasc national tillage conference. The highest number of attendees in recent years, many came seeking answers to the significant challenges and changes coming down the track for Ireland’s 14,000 tillage farmers.
The new-look conference gave a diverse range of research and agronomy updates throughout the day. This article will focus on the first half of the conference. The early-morning session focused on key pests, grassweeds and cereal disease resistance, and how to meet these challenges using integrated pest management (IPM). The later session focused on the environmental footprint and the role of cover crops in the sector.
Grain aphid resistance
The partial resistance to the pyrethroid insecticide group in Irish grain aphid populations was first discovered here in 2013. This SA3 clone showed varying degrees of resistance to the commonly used insecticides. This type of resistance is now commonly known as “knock-down resistance” (KDR), explained Dr Michael Gaffney. Since then, intensive field sampling and laboratory testing has shown that the SA3 clone can not only survive field rates of pyrethroids, but continue to reproduce after this exposure. Furthermore, a second known resistance mechanism has now been detected in Irish aphids.
This SA3 clone shows partial resistance to the insecticide group pyrethroids.
Around 50% of insecticide modes of action were lost in Ireland from 2008 to 2018. Combined with our poor ability to predict BYDV and the presence of SA3 clones, the industry was urged to adopt IPM approaches where possible. These include altering planting dates (later for winter, earlier for spring) and rotating our remaining insecticide classes.
Spread of grassweed resistance
Ronan Byrne delivered an insight into the spread of herbicide resistance in Irish wild oat populations. The spring germinating plant is a formidable weed in Irish tillage fields due to its staggered germinating window and aggressive growth pattern.
Ronan explained that until recently, the prevalence of resistance in Irish wild oat populations was unknown. His work, which centred on a large-scale study in Co Wexford across 102 fields, sampling wild oat populations, sought to change this. Thirty-six of the 102 samples were tested for resistance to the ACCase inhibiting herbicides, fenoxaprop (Foxtrot) and pinoxaden (Axial).
Around 55% of the samples tested positive for resistance to at least one of these herbicides. There were two main resistance mechanisms identified in these populations – target site and non-target site. Target site resistance is where a simple mutation stops the herbicide from binding to the target enzyme in the plant, causing resistance to specific herbicides. Different modes of action may still be effective.
Wild oats are a formidable weed in Irish tillage fields.
Non-target site resistance is an entirely different animal. It is caused when multiple minor genes build up, allowing the plant to metabolise herbicides gradually leading to resistance. The real challenge with this form of resistance is that it isn’t herbicide-specific, meaning that, in theory, some wild oat populations could already be resistant to herbicides which have not even been developed yet.
Ronan’s research found that resistance to both herbicides was clustered. This indicates that resistant seeds are spreading throughout the farming network via machinery, straw, grain, natural migration, etc.
Given the decreasing pool of herbicides and the increasing prevalence of resistance, the message is clear. Alternative methods of control, such as better rotations, vigilance with machinery hygiene, alternating chemistry, stale seedbeds, etc, are required at farm level.
Life after CTL
From 20 May of this year, chlorothalonil (CTL) will no longer be permitted for use in Ireland. As growers will know, our abundance of rainfall throughout the growing season in Ireland, enables septoria tritici blotch and ramularia leaf spot to thrive in winter wheat and spring barley respectively.
Steven Kildea explained that for both diseases the multi-site fungicide CTL has become key in control programmes over the past two decades. For septoria control, CTL was initially used as a tool in delaying the development and spread of fungicide resistance. However, more recently it has been important in providing direct control. For ramularia, it has been essential for the control of the disease almost since the recognition of the disease in the late 1990s/early 2000s, explained Steven. The loss of CTL represents a significant threat to short-term winter wheat and barley production in Ireland.
Ramularia will be a challenge to control post CTL.
Steven reminded attendees that no individual component of disease control will provide the solution post-CTL so an integrated approach must be taken.
In terms of septoria, he explained that variety resistance is improving on average, going from a 4 to a 5.5 resistance rating over the past number of years. Delaying drilling and manipulating canopy density will also help but there is a cost benefit to this.
For ramularia, less information is known on control measures for the disease. However, variety resistance and minimising plant stresses during the growing season will become fundamental to delaying the development of this disease.
New products are coming to the market which show promise against both diseases. However, if they are to be protected the above tactics will become essential components of disease control programmes and will need to be tailored to the crop.
Tillage environmentally sustainable
It is no surprise that sustainability was a key theme of this year’s conference. Attendees heard from Karl Richards that greenhouse gasses (GHG) in agriculture have increased in recent years, mainly due to dairy expansion. Agricultural emissions are dominated by CH4 (methane) and N2O (nitrous oxide) and now account for 32% of national emissions. As a result, agriculture must reduce emissions of CH4, N2O and CO2 (carbon dioxide) by 10% to 17.5 -19Mt CO2 equivalent and deliver carbon sequestration of 10% (2.7 Mt CO2e) by 2030.
However, the tillage sector stacks up extremely well in the face of these emissions, accounting for just 8% of agricultural emissions (2.56% of national emissions). As a result, the carbon footprint of the main Irish tillage crops is low, ranging from 0.3kg to 0.6kg of CO2 per kg grain. Within the sector’s emission profile, animals within tillage enterprises represent the main source of GHGs.
The loss of CTL represents a significant threat to short-term winter wheat and barley production in Ireland
That doesn’t mean tillage won’t have to contribute to both our reduction and sequestration targets. However, Karl explained that there are a lot of synergy between improving productivity and improving sustainability on tillage farms.
Reducing nitrogen fertiliser use and associated emissions and increasing soil organic matter levels and carbon sequestration will be achieved through the application of organic manures, use of cover crops, straw incorporation, minimum tillage and expanded rotations. For example, applying farmyard manure at a rate of 25t/ha will add around 2.5t of carbon per ha. Growing cover crops also increases soil organic carbon by around 10t to 15t of carbon per ha over 20 to 40 years.
Oilseed rape
establishment
optimisation
Oilseed rape (OSR) represents an important break crop for many Irish growers. Teagasc’s Dermot Forristal gave an insight into some of OSR establishment, agronomic and emissions research undertaken at Teagasc.
In the first of three trials reported, Dermot explained how the sowing widths and seed rates affect yields. The trials looked at seeding row widths from 125mm to 750mm and seeding rates of 10 to 60 seeds. Results indicated that seeding row widths of up to 500mm did not result in a negative impact on yield, although sowing at 750mm did. The use of different seed rates did not impact on the row width results. However, if green area indices in spring were to be low (<0.25), higher seed rates recover faster.
The second trial compared establishment systems looking at a plough-based system with 125mm and 600mm row widths; a min-till system with 125mm and 600mm sowing widths and strip tillage with just 600mm row widths.
Non-plough systems do result in reduced soil carbon loss at cultivation, however, there is little difference in cumulative CO2 losses when compared to min-till or strip-till.
The plough-based establishment system often resulted in the highest plant populations – in six of eight comparisons this had no effect on crop yield. On two occasions, plough-established crops did yield better than strip-tillage, however. Overall, Dermot explained that there is scope to save costs and time when establishing OSR through reduced cultivation systems and reduced seed rates when conditions are right.
While non-plough systems did result in reduced soil carbon loss at cultivation, there was little difference in cumulative CO2 losses. Work also showed that winter OSR took in 5.3t of carbon/ha (February to July), well above the average of 2.8t carbon/ha for all crops. Of this 2.84t carbon/ha was retained post-harvest.
N2O losses were greater with low-disturbance tillage systems due to slightly higher soil moistures but emissions were low. Changes in rotation and soil cultivation were also seen to benefit the microbial communities in soil and, in turn, reduced take-all.
Denmark
Catch crops are set to play a more prominent role in Irish tillage farming, partly due to our carbon sequestration targets. Nanna Hellum Kristensen of SEGES Denmark gave attendees an insight into the role of catch crops in that country.
In 1999, in response to increasing nitrogen losses from farmland, mandatory establishment of catch crops was introduced in Denmark, requiring 10% of the area on tillage farms and 14% of the area on livestock farms to be planted with catch crops. Since then, this requirement has grown to as high as 30% on tillage and 50% on livestock farms in some areas.
There are tough restrictions on the species which they are allowed to sow, with no legumes allowed. Nanna explained that growers there have difficulty in establishing cover crops in challenging years, as in Ireland.
Catch crops will play an more important role in Irish farming.
Typical establishment methods include undersowing grass, broadcasting seed two to three weeks pre-harvest and sowing post-harvest.
Field trials completed by SEGES showed that the catch crops release nitrogen to the following crop. However, the amount is highly dependent on the year and soil type. Her trial work in 2018/2019, found the amount of nitrogen saved for the following spring crop after a mixture of fodder radish and phacelia was 20kg N/ha. After mixtures, including nitrogen fixating species such as vetch, as much as 40- 50kg was available to the following crop. Both mixtures were found to have a positive correlation on yield for the following spring crop. These results are based on crops established on sandy soils. On clay soils she said it was more difficult to find significant results.
Irish perspective
However, Teagasc’s Richie Hackett presented data from trial work on catch crops at Oak Park. He explained that in general, the effects of non-leguminous catch crops compared to bare fallow or natural regeneration on yields of following cereal crops were variable, often small and sometimes negative. Significant yield benefits in succeeding crops following catch crops occurred infrequently.
Most of the trial work in Oak Park used single species cover crops.
Given that sown catch crops incur seed costs, establishment costs and destruction costs, and have limited effects on subsequent cereal yields, the use of sown species of catch crops is often not economically justified.
Catch crops are set to play a more prominent role in Irish tillage farming, partly due to our carbon sequestration targets
In work done on light soil in Oak Park, positive yield results from single species cover crops were recorded in trials but were very variable. The yield benefit was even more variable on medium soils, with occasional yield reductions.
However, cover crops provide a host of other potential environmental benefits he said, including reducing nutrient loss, improving soil heath and structure and preventing erosion, for example.
He also added that blanket recommendations for cover crops were difficult, as outcomes depended on a range of factors including species, soil type, weather, rotation, etc.
Initial experiments with leguminous cover crops suggest that they may have considerable potential to reduce the fertiliser nitrogen requirements of crops under Irish conditions. However, results are variable.
More from the National Tillage Conference to come.
Read more
Launch of new Corteva fungicide Inatreq delayed until 2021
Tillage has important role to play in carbon sequestration – Teagasc conference
Crowds of over 400 growers and members of the industry descended on Kilkenny last week for this year’s Teagasc national tillage conference. The highest number of attendees in recent years, many came seeking answers to the significant challenges and changes coming down the track for Ireland’s 14,000 tillage farmers.
The new-look conference gave a diverse range of research and agronomy updates throughout the day. This article will focus on the first half of the conference. The early-morning session focused on key pests, grassweeds and cereal disease resistance, and how to meet these challenges using integrated pest management (IPM). The later session focused on the environmental footprint and the role of cover crops in the sector.
Grain aphid resistance
The partial resistance to the pyrethroid insecticide group in Irish grain aphid populations was first discovered here in 2013. This SA3 clone showed varying degrees of resistance to the commonly used insecticides. This type of resistance is now commonly known as “knock-down resistance” (KDR), explained Dr Michael Gaffney. Since then, intensive field sampling and laboratory testing has shown that the SA3 clone can not only survive field rates of pyrethroids, but continue to reproduce after this exposure. Furthermore, a second known resistance mechanism has now been detected in Irish aphids.
This SA3 clone shows partial resistance to the insecticide group pyrethroids.
Around 50% of insecticide modes of action were lost in Ireland from 2008 to 2018. Combined with our poor ability to predict BYDV and the presence of SA3 clones, the industry was urged to adopt IPM approaches where possible. These include altering planting dates (later for winter, earlier for spring) and rotating our remaining insecticide classes.
Spread of grassweed resistance
Ronan Byrne delivered an insight into the spread of herbicide resistance in Irish wild oat populations. The spring germinating plant is a formidable weed in Irish tillage fields due to its staggered germinating window and aggressive growth pattern.
Ronan explained that until recently, the prevalence of resistance in Irish wild oat populations was unknown. His work, which centred on a large-scale study in Co Wexford across 102 fields, sampling wild oat populations, sought to change this. Thirty-six of the 102 samples were tested for resistance to the ACCase inhibiting herbicides, fenoxaprop (Foxtrot) and pinoxaden (Axial).
Around 55% of the samples tested positive for resistance to at least one of these herbicides. There were two main resistance mechanisms identified in these populations – target site and non-target site. Target site resistance is where a simple mutation stops the herbicide from binding to the target enzyme in the plant, causing resistance to specific herbicides. Different modes of action may still be effective.
Wild oats are a formidable weed in Irish tillage fields.
Non-target site resistance is an entirely different animal. It is caused when multiple minor genes build up, allowing the plant to metabolise herbicides gradually leading to resistance. The real challenge with this form of resistance is that it isn’t herbicide-specific, meaning that, in theory, some wild oat populations could already be resistant to herbicides which have not even been developed yet.
Ronan’s research found that resistance to both herbicides was clustered. This indicates that resistant seeds are spreading throughout the farming network via machinery, straw, grain, natural migration, etc.
Given the decreasing pool of herbicides and the increasing prevalence of resistance, the message is clear. Alternative methods of control, such as better rotations, vigilance with machinery hygiene, alternating chemistry, stale seedbeds, etc, are required at farm level.
Life after CTL
From 20 May of this year, chlorothalonil (CTL) will no longer be permitted for use in Ireland. As growers will know, our abundance of rainfall throughout the growing season in Ireland, enables septoria tritici blotch and ramularia leaf spot to thrive in winter wheat and spring barley respectively.
Steven Kildea explained that for both diseases the multi-site fungicide CTL has become key in control programmes over the past two decades. For septoria control, CTL was initially used as a tool in delaying the development and spread of fungicide resistance. However, more recently it has been important in providing direct control. For ramularia, it has been essential for the control of the disease almost since the recognition of the disease in the late 1990s/early 2000s, explained Steven. The loss of CTL represents a significant threat to short-term winter wheat and barley production in Ireland.
Ramularia will be a challenge to control post CTL.
Steven reminded attendees that no individual component of disease control will provide the solution post-CTL so an integrated approach must be taken.
In terms of septoria, he explained that variety resistance is improving on average, going from a 4 to a 5.5 resistance rating over the past number of years. Delaying drilling and manipulating canopy density will also help but there is a cost benefit to this.
For ramularia, less information is known on control measures for the disease. However, variety resistance and minimising plant stresses during the growing season will become fundamental to delaying the development of this disease.
New products are coming to the market which show promise against both diseases. However, if they are to be protected the above tactics will become essential components of disease control programmes and will need to be tailored to the crop.
Tillage environmentally sustainable
It is no surprise that sustainability was a key theme of this year’s conference. Attendees heard from Karl Richards that greenhouse gasses (GHG) in agriculture have increased in recent years, mainly due to dairy expansion. Agricultural emissions are dominated by CH4 (methane) and N2O (nitrous oxide) and now account for 32% of national emissions. As a result, agriculture must reduce emissions of CH4, N2O and CO2 (carbon dioxide) by 10% to 17.5 -19Mt CO2 equivalent and deliver carbon sequestration of 10% (2.7 Mt CO2e) by 2030.
However, the tillage sector stacks up extremely well in the face of these emissions, accounting for just 8% of agricultural emissions (2.56% of national emissions). As a result, the carbon footprint of the main Irish tillage crops is low, ranging from 0.3kg to 0.6kg of CO2 per kg grain. Within the sector’s emission profile, animals within tillage enterprises represent the main source of GHGs.
The loss of CTL represents a significant threat to short-term winter wheat and barley production in Ireland
That doesn’t mean tillage won’t have to contribute to both our reduction and sequestration targets. However, Karl explained that there are a lot of synergy between improving productivity and improving sustainability on tillage farms.
Reducing nitrogen fertiliser use and associated emissions and increasing soil organic matter levels and carbon sequestration will be achieved through the application of organic manures, use of cover crops, straw incorporation, minimum tillage and expanded rotations. For example, applying farmyard manure at a rate of 25t/ha will add around 2.5t of carbon per ha. Growing cover crops also increases soil organic carbon by around 10t to 15t of carbon per ha over 20 to 40 years.
Oilseed rape
establishment
optimisation
Oilseed rape (OSR) represents an important break crop for many Irish growers. Teagasc’s Dermot Forristal gave an insight into some of OSR establishment, agronomic and emissions research undertaken at Teagasc.
In the first of three trials reported, Dermot explained how the sowing widths and seed rates affect yields. The trials looked at seeding row widths from 125mm to 750mm and seeding rates of 10 to 60 seeds. Results indicated that seeding row widths of up to 500mm did not result in a negative impact on yield, although sowing at 750mm did. The use of different seed rates did not impact on the row width results. However, if green area indices in spring were to be low (<0.25), higher seed rates recover faster.
The second trial compared establishment systems looking at a plough-based system with 125mm and 600mm row widths; a min-till system with 125mm and 600mm sowing widths and strip tillage with just 600mm row widths.
Non-plough systems do result in reduced soil carbon loss at cultivation, however, there is little difference in cumulative CO2 losses when compared to min-till or strip-till.
The plough-based establishment system often resulted in the highest plant populations – in six of eight comparisons this had no effect on crop yield. On two occasions, plough-established crops did yield better than strip-tillage, however. Overall, Dermot explained that there is scope to save costs and time when establishing OSR through reduced cultivation systems and reduced seed rates when conditions are right.
While non-plough systems did result in reduced soil carbon loss at cultivation, there was little difference in cumulative CO2 losses. Work also showed that winter OSR took in 5.3t of carbon/ha (February to July), well above the average of 2.8t carbon/ha for all crops. Of this 2.84t carbon/ha was retained post-harvest.
N2O losses were greater with low-disturbance tillage systems due to slightly higher soil moistures but emissions were low. Changes in rotation and soil cultivation were also seen to benefit the microbial communities in soil and, in turn, reduced take-all.
Denmark
Catch crops are set to play a more prominent role in Irish tillage farming, partly due to our carbon sequestration targets. Nanna Hellum Kristensen of SEGES Denmark gave attendees an insight into the role of catch crops in that country.
In 1999, in response to increasing nitrogen losses from farmland, mandatory establishment of catch crops was introduced in Denmark, requiring 10% of the area on tillage farms and 14% of the area on livestock farms to be planted with catch crops. Since then, this requirement has grown to as high as 30% on tillage and 50% on livestock farms in some areas.
There are tough restrictions on the species which they are allowed to sow, with no legumes allowed. Nanna explained that growers there have difficulty in establishing cover crops in challenging years, as in Ireland.
Catch crops will play an more important role in Irish farming.
Typical establishment methods include undersowing grass, broadcasting seed two to three weeks pre-harvest and sowing post-harvest.
Field trials completed by SEGES showed that the catch crops release nitrogen to the following crop. However, the amount is highly dependent on the year and soil type. Her trial work in 2018/2019, found the amount of nitrogen saved for the following spring crop after a mixture of fodder radish and phacelia was 20kg N/ha. After mixtures, including nitrogen fixating species such as vetch, as much as 40- 50kg was available to the following crop. Both mixtures were found to have a positive correlation on yield for the following spring crop. These results are based on crops established on sandy soils. On clay soils she said it was more difficult to find significant results.
Irish perspective
However, Teagasc’s Richie Hackett presented data from trial work on catch crops at Oak Park. He explained that in general, the effects of non-leguminous catch crops compared to bare fallow or natural regeneration on yields of following cereal crops were variable, often small and sometimes negative. Significant yield benefits in succeeding crops following catch crops occurred infrequently.
Most of the trial work in Oak Park used single species cover crops.
Given that sown catch crops incur seed costs, establishment costs and destruction costs, and have limited effects on subsequent cereal yields, the use of sown species of catch crops is often not economically justified.
Catch crops are set to play a more prominent role in Irish tillage farming, partly due to our carbon sequestration targets
In work done on light soil in Oak Park, positive yield results from single species cover crops were recorded in trials but were very variable. The yield benefit was even more variable on medium soils, with occasional yield reductions.
However, cover crops provide a host of other potential environmental benefits he said, including reducing nutrient loss, improving soil heath and structure and preventing erosion, for example.
He also added that blanket recommendations for cover crops were difficult, as outcomes depended on a range of factors including species, soil type, weather, rotation, etc.
Initial experiments with leguminous cover crops suggest that they may have considerable potential to reduce the fertiliser nitrogen requirements of crops under Irish conditions. However, results are variable.
More from the National Tillage Conference to come.
Read more
Launch of new Corteva fungicide Inatreq delayed until 2021
Tillage has important role to play in carbon sequestration – Teagasc conference
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