Mitigating winter oilseed rape establishment risks will be at the forefront of growers’ minds as they plan next year’s rotations and varieties. Farmers Guardian looks at how to get crops off to the best start this autumn.
For the best chance of establishing a good crop, farmers preparing to plant oilseed rape in August and September are being advised to follow a five-point plan.
With many growers poring over their variety choice, United Oilseeds managing director Chris Baldwin says getting crops out of the ground quickly to grow away from pests such as flea beetle is a priority but not the only consideration.
He says: “Turnip yellows virus (TuYV) can also be a significant cause of yield loss, so choosing a resistant variety can be a big help in safeguarding yields. A number of new hybrid varieties on the market are ‘trait-loaded’, offering protection from some yield-robbing diseases, such as light leaf spot and TuYV.”
Simon Kightley, oilseed rape expert at NIAB, believes early drilling is important, but only when there is good moisture availability.
He says: “Drilling when there is sufficient moisture for germination is critical. Lack of moisture prevents uniform emergence and stops the seedlings from growing away quickly, giving more time for flea beetles to attack.”
Using the right establishment technique, taking account of soil conditions, is also important, he adds.
“A well compacted seedbed after drilling will help to retain soil moisture and promote rapid germination and emergence.”
Seed rates could increase from their current low of 40 plants/sq.m to 60 plants/sq.m to suit today’s more challenging growing environment.
Growers frustrated with cabbage stem flea beetle (CSFB) attacks on establishing crops should think carefully about their insecticide applications.
Mr Kightley adds: “The temptation to repeat sprays should be questioned. If pyrethroids do not produce a good result the first time, repeat sprays are doing more harm than good, especially to beneficial arthropods which predate flea beetle.”
William Marsden of Marston Farms, Pembrokeshire, and Agrii Agronomist Dai Llewellyn have shown how flexible you can be with hybrid winter oilseed rape, drilling it on October 5.
Mr Llewellyn says: “If conditions are right it is fairly common for us to drill a lot of winter oilseed rape at the end of September. I have drilled in the first couple of days of October successfully before, however, it has got to be a hybrid and it has got to be vigorous.
"We chose InV1035 because, of all the hybrids I am involved with growing, this is the fastest developing variety in autumn and spring.”
Mr Llewellyn explains his reasoning behind late drilling.
“We had already sown 40 hectares of winter OSR which had been planted in the second week of September and established well. A 20ha block on Mr Marsden’s Crickmaram Farm was destined to be spring cropped but at the end of September we looked at the gross margin for the spring break crop and the numbers were not good so we thought we would have a go at growing late-drilled hybrid OSR.”
Drilling conditions were good and the sandy loam soil was lightly cultivated. Three fields of InV1035, which followed wheat, were drilled with a Pottinger Terrasem at 50 seeds/sq.m.
Mr Llewellyn says: “By the time we put the herbicide on it in mid December, there was not much difference between the InV1035 and other varieties grown on the farm which were sown at a more normal sowing date.
“We are fortunate we have had no problem with cabbage stem flea beetle on this farm, although it is now beginning to be an issue here in Wales.”
For many growers, CSFB means getting oilseed rape established is difficult, and in some cases impossible. This year, adult feeding damage was only part of the problem. Large numbers of larvae in the plant then inhibited growth and development of crops in the spring, resulting in thousands of acres lost to this pest.
ADAS entomologist Dr Sacha White is lead researcher on the AHDB Cereals and Oilseeds-funded project which collected 14 years of data from more than 1,600 sites across England and Scotland on CSFB adult damage and larval populations.
He says: “September sowing correlated significantly with lower larval populations in autumn and spring. If you have an early-August drilled crop then CSFB is likely to be in that crop longer, feeding earlier and egg laying earlier.
"In some ways, losing the crop to larvae is worse than losing it to adult damage because by that stage there has been greater investment in the crop and there are fewer redrill options.”
With 160 hectares of OSR near Yeovil on the Somerset/Dorset border, Chris Tanswell and his son Ian, of Manor Contracting, are delaying drilling until September and moving to more vigorous, faster-developing varieties in a programme they are implementing with Agrii agronomists Mathew Hutchings and Todd Jex.
With a consistent annual OSR yield average of just less than 5 tonnes per hectare at 46-47 per cent oil, Chris is looking for new ways to boost the crop’s performance.
Switching about 40 per cent of the crop from an all-conventional variety mix into Clearfield OSR to combat growing problems with charlock, runch, hedge mustard and swinecress on one of the farms has been a real eye-opener, Mr Hutchings says.
“We have been impressed with the vigour of DK Imperial, in particular. Especially because we are deliberately delaying drilling from mid-August to early September so the crops only emerge after the peak of flea beetle migration.
"Our Dorset iFarm work over several years shows this really helps reduce problems from both adult beetles and larvae.
“The Imperial came through the ground and grew away from the cotyledon stage noticeably quicker than anything else from the later sowing, with tremendous rooting. This is just what we need to keep well ahead of the beetle, not to mention slugs and pigeons.”
The Manor Contracting team says the imazamox resistance Clearfield varieties carry is helping to deal with any sulphonylurea residues from their weed control in preceding barley crops, while herbicide spend can be held back until the rape is well-established, targeting weeds using a low rate of clomazone pre-emergence to prevent early chickweed and cleavers growth compromising crop establishment.
Chris says: “It also means we do not have to use bifenox any longer. Because the season was so dry we did not spray the Cleravo until early November when we had sufficient weed growth. It is something we will only use if and when we need it.”
Delayed drilling is also helping with pre-planting weed and volunteer barley control. Once the cereal straw has been baled and cleared, the ground is cultivated with a Discaerator and left for as long as possible.
“This is a marvellous tool,” Chris says. “We vary our cultivation depth between seven to 12 inches to achieve the best structuring of our wide range of soils, from Yeovil sand to heavy yellow clay. The lighter ground then settles nicely while the heavy ground weathers down. Then it is in with the glyphosate before minimum disturbance drilling.”
DAP is then appliead at a rate of 150kg/ha as soon as the crop comes through the ground, as well as 30kg/ha of nitrogen.
While the current recipe appears to be working well, Chris and Ian are keen to explore additional options.
Based on Agrii trials work at the Dorset iFarm, they are looking at drilling a companion crop, such as buckwheat or berseem clover, with their OSR and applying either cattle slurry or a garlic spray as the crop emerges.
“We have found all three methods can help,” says Mr Jex.
“They seem to confuse the pest by disguising the crop, either in appearance or smell. They only provide a respite of up to two weeks. But this can be critical in allowing the crop to get away.”
Even last year’s ‘Beast from the East’ and the cruel drought which followed did little to dent yields on Tim Booth’s 360-hectare arable farm at Fenhouses, Swineshead, Lincolnshire.
And although flea beetle has become a problem in the area, his crops are proving remarkably resilient.
“It is only recently I have really started to fully understand the relationship between the space plants need to develop fully, how to get them to establish reliably and the key role the variety plays in all this,” says Mr Booth.
“It is certainly not easy. You can think you have a great looking oilseed rape crop but in reality it is too thick and most of the pods are at the top of the plant. Unfortunately, you often only realise this at harvest when the yields turn out to be lower than you had anticipated.
“You are usually much better off with fewer plants which can develop properly and have canopies which allow light to penetrate properly through them so pods mature at all levels.”
An advocate of early drilling, Mr Booth says the results achieved at harvest are directly related to the decisions made at establishment with ‘less is more’ often the best approach.
“Last year, for example, we drilled a field of Kielder on August 19 with a single pass using a Simba five-tine drill followed by light rolling. It is visibly the most consistent looking crop we have ever grown in what has historically been a troublesome field.
“We are using 24in spacing and this, combined with our efforts to move soil as little as possible, means the plants established quickly and have the space to grow well subsequently.
“You can see the stalks are noticeably thicker than more closely drilled crops, which is good for standing power and lodging resistance, but you can see the pods forming right down to the base of the plant.
“We have consistently achieved oil contents of about 45 per cent with Elgar and yields of 4.5 tonnes/ha, including last year when yields were below 3t/ha for many of our other varieties. We have hit more than 5t/ha in some fields, but it is the average which is more important to me.
“Elgar has looked good all through the growing season but the Kielder looked exceptional, even and strong with just the right plant population and canopy structure so I am confident it will yield well.”