Arable News

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OSR – Finding the best solution for water

Crop protection company MAUK hosted a technical briefing in Cambridge recently focusing on a sustainable approach to maximising the potential of oilseed rape

Crop protection company Makhteshim Agan (MAUK) hosted a technical briefing in Cambridge recently focusing on a sustainable approach to maximising the potential of oilseed rape. Dominic Kilburn reports.Learning from the lessons of weed control strategies in cereal crops could result in better control of black-grass when targeted in oilseed rape, in addition to minimising the risk of pesticide losses to water.They were the main messages from MAUK’s technical lead, Dr Paul Fogg (left) who began by emphasising that ‘problem pesticides’ being found in water could result in complete product withdrawal in some cases. “The frequency and magnitude of herbicides including metazachlor, carbetamide and propyzamide being found in surface water is unsustainable and, under the Water Framework Directive, we could see restrictions or withdrawals having serious implications on the ability to control black-grass in the rotation,” he stressed.Paul said that 40 per cent of the oilseed rape growing area in the UK suffered with black-grass and the loss of key herbicides and resultant poor control, could mean that OSR gross margins, currently some of the best available, are reduced by as much as 43 per cent.”Issues with certain herbicides are coming to the fore and we will have to expect gross margin losses from poor black-grass control unless we get to grips with it now,” he added.Paul said that it was a myth that soils needed to be cold and wet to best suit OSR herbicide efficacy and this had driven the traditional November and later-applied treatments for black-grass control. He used the example of carbetamide, a product that was often used in the late autumn slot to fire-fight black-grass, which found its way into water via field drainage systems running at their peak. “This situation is unsustainable and it is something we are trying to change,” pointed out Paul.”In cereals we target black-grass earlier in the season but with oilseed rape we target it late with residuals, and it doesn’t make sense. “We should be using the best chemistry available to manage black-grass across the rotation and applying the lessons learned in cereals. We should be targeting small, shallow black-grass early with residual stacking and applying it to the soil – that’s where we should use it.”Paul suggested that following the conditions experienced by many last year, growers this autumn will be desperate to get crops in the ground as soon as they can after harvest. With oilseed rape there is generally no opportunity for control of black-grass via stale seedbeds due to the quick turnaround time. “Current strategies generally start with a metazachlor application at pre- or early post-emergence which will provide 10-30 per cent black-grass control, and this is usually followed by contact sprays in mid-September where there are known resistance issues. “Residuals are then applied from early November to tillered, deep-rooting black-grass and when large canopies are an issue,” he pointed out.”We are suggesting that the residual application of Crawler (carbetamide) should be brought forward by two months and targeting black-grass at the 1-2 leaf stage when the plants have a shallow root system. Carbetamide is taken up through the roots and shoots and small, actively growing black-grass will take up a lethal dose faster than slow growing, or dormant plants,” he explained.By bringing the timing forward, Paul said that the application rate could be reduced from its recommended 3.5kg/ha, when conditions were cold and wet in late autumn, down to 2.5kg/ha at a mid-September timing, once the oilseed rape crop is at 3-4 leaves.”Carbetamide will do its job in a short time and any residues left in the soil will degrade before it gets too wet,” he added.Paul said that the mid-September Crawler application would be followed by Cohort (propyzamide) in November as a twin residual approach.
MAUK trials in 2012 showed a good level of black-grass control with carbetamide when used as part of a sequence across a range of soil moistures from dry to saturated, and it gave better control of black-grass under ‘normal’, ‘dry’ and ‘very dry’ soil moisture conditions compared with propyzamide.When considering control of black-grass emerging from depth, trials also showed that carbetamide gave good control down to a depth of 7.5cm, while propyzamide gave poor control at emergence depths greater than 2.5cm. “Carbetamide is water soluble and can move within the soil profile even when sprayed early,” added Paul.”Why delay applications if you have black-grass plants that you could control while they are small?” he questioned, adding that it is only the persistency of carbetamide, not the efficacy, that is affected by warmer temperatures found earlier in the season. “As soon as the crop is at the 3-4 leaf stage then start the programme with carbetamide at 2.5kg/ha. A twin residual approach will improve black-grass control in oilseed rape and the earlier timing of Crawler will reduce losses to surface water considerably.”Environment Agency viewpoint
There must be an improvement in the level of some pesticides being found in water otherwise a more targeted range of measures, including limiting the use of certain pesticides in certain areas, may be implemented. That was the message delivered by the Environment Agency’s senior adviser (Pesticides) Jo Kennedy (left), whose presentation was pre-recorded and played to delegates especially for the event.She explained that the Water Framework Directive is asking that the level of pesticides being found at some drinking water treatment plants is reduced to avoid the need for extra treatment. “We’ve got to a certain point with voluntary measures but we need to do more in some areas of the country that are particularly at risk,” she said.Prime ‘red zone’ pesticides causing non-compliance in surface waters included slug pellet active metaldehyde (the number one culprit), but also oilseed rape herbicides; metazachlor, propyzamide and carbetamide.In addition, chlorotoluron and some grassland herbicides were included in a group where “progress had to be made”. She acknowledged that voluntary measures through Catchment Sensitive Farming and the Voluntary Initiative were on-going, but also that in some higher risk catchments this current suite of measures would not necessarily be sufficient to achieve compliance – primarily because of catchment characteristics such as soil type, drainage and cropping patterns. Part of the solution, she said, is about better catchment characterisation and a hierarchy of measures – with extra measures being implemented in higher risk locations. Farmers in areas at risk need to think about what else they could do to make a difference, such as employing alternative crop rotations, using bio-beds, buffer zones and precision application methods, she explained.A Defra project has also recently been undertaken to help identify the best way forward in higher risk catchments, she pointed out. Consultants worked with stakeholders from the agricultural sector and water industry to identify measures and implementation mechanisms, and cost out various options including product restrictions and the catchment measures already mentioned. “The report will be published later this summer and discussions continue with the agricultural sector and water industry over the best solutions for protecting water while also ensuring sustainable food and farming can be identified. “Even if you are not in a ‘risk area’ it’s still very important to continue to farm using best practice to keep pesticides out of water and avoid deterioration in water quality,” she urged.Jo highlighted the Environment Agency’s ‘What’s in your backyard’ (WIYBY) website as a useful tool for farmers to find out if they are in a vulnerable zone, simply by entering their postcode.”Farmers and agronomists are all key to helping with this and we are engaging with crop protection companies to try and find other solutions to protect water.
“We’ve seen water companies work closely with the Metaldehyde Stewardship Group (MSG) to identify the catchments most at risk from metaldehyde and in those areas substitution to ferric phosphate products may prove to be the most cost-effective solution,” she said.”However, with oilseed rape herbicides there is a slightly different challenge in that there are no alternative products available. We must still employ a targeted approach and there is the need to think about cultural methods of controlling black-grass, for example, to reduce the reliance on oilseed rape herbicides, and we must think about applying them at different times to avoid the wettest weather.”I would encourage agronomists and farmers to use the relevant advice from the MSG and VI website. We need to work together to find the best solution for water,” she 


What’s OSR autumn vigour all about?
Autumn vigour in oilseed rape is far more about the time of, and conditions at, drilling rather than the name of the variety written on the side of the bag, said United Oilseeds’ technical manager, Richard Elsdon (left).He suggested that whether a conventional or hybrid variety, key to achieving good autumn vigour was down to the time of drilling, the condition of the soil, the right depth of planting, herbicide use and the application of seedbed fertiliser. “What is autumn vigour? Well, I would say that these are the factors that leaf production and size, as well as root development, depend on rather than a name on the bag,” he commented.Richard said that last season was a good example whereby conditions dictated crop performance, with any crops planted up until about the 4-5 September looking promising, but those drilled after that date, conventional or hybrid, have struggled.”There is certainly a huge variation in crops this season, but that is largely down to that early September cut-off planting time.
“Having six true leaves by Christmas is key in any season,” he added.As well as discussing autumn vigour, Richard reviewed some of the variety choices facing growers this season; PR46W21 and Marathon being two obvious, high yielding fully recommended options for the East/West region.He also pointed out that oil content was an area that growers may not factor in sufficiently each season; highlighting that PR46W21’s two per cent extra oil content over Marathon would currently be worth an extra 9.69/t – a factor worth considering when making variety selection.In terms of Candidate varieties to watch out for, Richard said that Charger (East/West) was a short and early conventional variety with “middle of the road” disease resistance. However, in Swedish verticillium trials it had only incurred a four per cent infection – scarcely anything, he stressed. “It also gave a yield of 7t/ha and, with potential for high yield, it could be one of the first varieties offering verticillium resistance,” he added.Semi-dwarf hybrid variety PX109 he described as a “possible game changer” with its low height (122cm) and high yield (104 E/W and 107 North). “With this type of variety offering a 10 per cent saving in diesel at harvest and an increase in combining speed, it would make me think. These types of plants have a very good rooting system and we picked this up when seeing it grown on poor land,” he said.Establishment focus
Soils First Farming and regular columnist in Farmers Guide, Steve Townsend (left) highlighted a number of areas that oilseed rape growers should focus their attentions on to improve crop establishment including good seed-to-soil contact in a fine, firm and moist seedbed, which is trash-, pest- and compaction-free, he said.Steve emphasised the importance of high organic matter levels in soils which can help improve the overall structure, reduce capping and slumping, retain moisture and resist compaction.”Long-term you will see the benefit from increased organic matter with more resilience in the soil,” said Steve.
“Chopping straw at harvest or returning FYM to the land will help encourage organic matter and reducing cultivation though minimum tillage will lessen oxidation losses,” he commented. “If you are finding last year’s residue when you cultivate, then you have been putting it too deep and roots won’t develop through it.”Chop and spread residue well with the combine and first cultivation pass. Mother nature leaves trash on the surface, but we seem to want to bury straw to make our machines work and expect oilseed rape to put up with the toxic effects of decaying straw.
“Are we cultivating for the good of the crop or are we doing it to enable the drill to work? If it’s the latter then the drill is managing the farm for you!”According to Steve, growers need a drill that can work in high trash or even direct drill – remembering that seed-to-soil contact is vital. Tined-based drills and cultivators handle the trash best, he noted, while minimising soil movement helps to keep the moisture in.
“The best chance of seed-to-soil contact is at around a depth of 2cm – that’s where the moisture is. If the moisture is deeper then put the seed in deeper.”He added that ‘smooth’ seedbeds are critical for delivering consistent depth placement and, as a result, more consistent rape establishment.
Consolidation post-drilling improves seed-to-soil contact as well as restricting slugs (see more on page 21), said Steve. “It also retains the moisture and draws moisture up to the rooting zone,” he added.He advises growers to roll twice, or more, using a heavy ring roller of between 0.6-0.8t/m to improve the germination of the rape.”It’s also important to consider nitrogen and phosphate applications at the critical 2-3 leaf stage of the crop as plants begin to look for soil-borne nutrition,” he concluded.

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