Article taken from the CPM, written by Tom Allen-Stevens and Rob Jones
Planting an autumn-sown cover crop, followed by spring wheat, has achieved the best result for controlling blackgrass at Agrovista’s Project Lamport site in Northants. The five-year rotational project with Bayer CropScience aims to test new concepts that go beyond the present techniques of stale seedbeds, delayed drilling and increasing the seed rate.
“There are 14 rotational plots, but the really interesting story is cover crops ahead of spring wheat,” commented Mark Hemmant of Agrovista.
Also in the field-scale trial plots are:
Highly resistant
The heavy land site was taken on in 2012 with a population of 2000 heads/m² of highly resistant blackgrass. “This was ploughed down and cropped with winter oilseed rape, which failed and was sprayed off, so effectively we had a year’s fallow,” explained Mark Hemmant. “But there was still a heavy blackgrass burden in autumn 2013.”
Of all the non-chemical control methods available, spring cropping is the most effective, according to work carried out by Stephen Moss and Peter Lutman at Rothamsted Research. “But it’s also challenging on heavy soil, and there are limited in-crop herbicides.”
So Agrovista asked French seed specialist Jouffray Drillaud to supply a cover crop that would make spring cropping more reliable on heavy soils. “We need a crop that dries the soil out at depth, but leaves a surface residue to keep moisture in the establishment zone. It should also bring soil structure benefits so we could direct drill the spring wheat – a priority so as not to create a seedbed for the blackgrass,” noted Mark Hemmant.
Cover crops are commonplace in France where there’s a restriction on leaving the land bare over winter. “But we turned a legal constraint into agronomic opportunity,” pointed out Jérȏme Vasseur of Jouffray Drillaud.
“Cover crops trap nitrogen otherwise leached over the winter, and then release it to the following crop – you can expect to recover 30kgN/ha. They also act as a green manure, raising levels of organic matter. The roots of the crop also improve the soil structure, and this results in less compaction.”
For effective blackgrass control, a cover crop has to be sowed later to allow for a stale seedbed, while it shouldn’t put on too much autumn growth to allow the blackgrass to germinate the autumn. It also has to provide a true break in the rotation, for both take-all and from brassicas, and be easy to destroy in the spring, and unlikely to cause a problem as a volunteer.
The seed mixture of choice was black oats and vetch. “Vetches are legumes that mineralise N fast, but have a low carbon:nitrogen ratio – that’s important, as the lower the ratio, the faster it release N to the soil in the spring,” continued Jérȏme Vasseur.
The black Strigosa oats have good rust resistance but an “explosive” autumn growth. “You want as much root biomass as possible to soak up the available N. There’s also a low sowing rate and small seed, which is important when mixing.”
In the Lamport trials, the structure of the soil that had the cover crop in spring was markedly improved, compared with the plot that was fallow, reported Mark Hemmant. “The fallow land was structureless – the rain had effectively bashed it down.”
Soil moisture probes revealed the soil was also drier at depth and retained more moisture in the establishment zone. “But the difference in the blackgrass population is very evident – after an autumn fallow, the crop of spring wheat had 15.3 blackgrass plants/m² in May, while after the cover crop there were just 4.3 plants/m².”
Jouffray Drillaud also supplies Agrovista with seed for companion crops. Drilled with OSR, these are a mixture of vetch and Berseem clover that help the crop establish, capture N and have been shown to improve yield by 0.2-0.3t/ha said Jérȏme Vasseur.
“The Berseem clover is very good at rooting, which helps the OSR – a very lazy rooter – to establish. A suitable mix for heavy land would be one vetch with two clovers, planted in the same row, although you could plant them in alternative rows with the OSR.
“They help to smother weeds and improve the soil structure, releasing around 30kgN/ha to the crop when they die back. That usually happens at the first hard frost, although if they survive the winter, clopyralid will take them out. But you can apply metazachlor and propyzamide to the crop without damaging the companion plants,” he noted.
Planting an autumn-sown cover crop, followed by spring wheat, has achieved the best result for controlling blackgrass at Agrovista’s Project Lamport site in Northants. The five-year rotational project with Bayer CropScience aims to test new concepts that go beyond the present techniques of stale seedbeds, delayed drilling and increasing the seed rate.
“There are 14 rotational plots, but the really interesting story is cover crops ahead of spring wheat,” commented Mark Hemmant of Agrovista.
Also in the field-scale trial plots are:
Sept vs Oct drilled winter wheat
Fallow
Hybrid rye, whole-cropped for anaerobic digestion
Spring wheat after stale seedbeds
Cover crops – both during autumn and spring
Highly resistant
The heavy land site was taken on in 2012 with a population of 2000 heads/m² of highly resistant blackgrass. “This was ploughed down and cropped with winter oilseed rape, which failed and was sprayed off, so effectively we had a year’s fallow,” explained Mark Hemmant. “But there was still a heavy blackgrass burden in autumn 2013.”
Of all the non-chemical control methods available, spring cropping is the most effective, according to work carried out by Stephen Moss and Peter Lutman at Rothamsted Research. “But it’s also challenging on heavy soil, and there are limited in-crop herbicides.”
So Agrovista asked French seed specialist Jouffray Drillaud to supply a cover crop that would make spring cropping more reliable on heavy soils. “We need a crop that dries the soil out at depth, but leaves a surface residue to keep moisture in the establishment zone. It should also bring soil structure benefits so we could direct drill the spring wheat – a priority so as not to create a seedbed for the blackgrass,” noted Mark Hemmant.
Cover crops are commonplace in France where there’s a restriction on leaving the land bare over winter. “But we turned a legal constraint into agronomic opportunity,” pointed out Jérȏme Vasseur of Jouffray Drillaud.
“Cover crops trap nitrogen otherwise leached over the winter, and then release it to the following crop – you can expect to recover 30kgN/ha. They also act as a green manure, raising levels of organic matter. The roots of the crop also improve the soil structure, and this results in less compaction.”
For effective blackgrass control, a cover crop has to be sowed later to allow for a stale seedbed, while it shouldn’t put on too much autumn growth to allow the blackgrass to germinate the autumn. It also has to provide a true break in the rotation, for both take-all and from brassicas, and be easy to destroy in the spring, and unlikely to cause a problem as a volunteer.
The seed mixture of choice was black oats and vetch. “Vetches are legumes that mineralise N fast, but have a low carbon:nitrogen ratio – that’s important, as the lower the ratio, the faster it release N to the soil in the spring,” continued Jérȏme Vasseur.
The black Strigosa oats have good rust resistance but an “explosive” autumn growth. “You want as much root biomass as possible to soak up the available N. There’s also a low sowing rate and small seed, which is important when mixing.”
In the Lamport trials, the structure of the soil that had the cover crop in spring was markedly improved, compared with the plot that was fallow, reported Mark Hemmant. “The fallow land was structureless – the rain had effectively bashed it down.”
Soil moisture probes revealed the soil was also drier at depth and retained more moisture in the establishment zone. “But the difference in the blackgrass population is very evident – after an autumn fallow, the crop of spring wheat had 15.3 blackgrass plants/m² in May, while after the cover crop there were just 4.3 plants/m².”
Jouffray Drillaud also supplies Agrovista with seed for companion crops. Drilled with OSR, these are a mixture of vetch and Berseem clover that help the crop establish, capture N and have been shown to improve yield by 0.2-0.3t/ha said Jérȏme Vasseur.
“The Berseem clover is very good at rooting, which helps the OSR – a very lazy rooter – to establish. A suitable mix for heavy land would be one vetch with two clovers, planted in the same row, although you could plant them in alternative rows with the OSR.
“They help to smother weeds and improve the soil structure, releasing around 30kgN/ha to the crop when they die back. That usually happens at the first hard frost, although if they survive the winter, clopyralid will take them out. But you can apply metazachlor and propyzamide to the crop without damaging the companion plants,” he noted.