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December 19, 2013

Protecting our OSR yield potential

West Midlands agronomist, Harry Abell reports on oilseed rape development and management priorities.

It may be coming up to Christmas but, with the winter refusing to reliably set-in, both our oilseed rape and the weeds are continuing to grow. And we certainly can’t write-off threats from disease or slugs just yet either. So we remain on full alert to do everything we can to protect the yield potential this season’s far better establishment has given us.

We’re glad we’ve concentrated on fast-developing, robust hybrids like DK ExPower and DK Excellium. As well as establishing strongly – even from later sowing on trickier ground – their phoma resistance has provided us with just the flexibility we needed in a season in which good fungicide spraying days have again been hard to find for many. There have been some filthy crops of more susceptible varieties about. They may be big enough to avoid serious stem canker problems, but this level of infection is bound to have an impact.

A good dose of metconazole has helped keep our earlier sown, better grown OSR from becoming too frothy. In most cases we combined this with prothioconazole to tackle early, though thankfully very localised, light leaf spot infections. We’ve definitely seen more LLS across our patch in recent years where rotations are tighter and we know we need to keep well on top of this wherever the weather stays mild. With this in mind, prothioconazole will be our fungicide of choice for the spring with added metconazole should we need further growth regulation.

Except for some very dry seedbeds where the pre-ems didn’t deal with mayweed and poppies as well as they might, weed control has been very good so far. As many chemicals in our post-em armoury are proving next to useless against black-grass these days the arrival of clethodim has been a real saviour.  To make the most of it for as long as we can, though, we’re being careful to maintain a good propyzamide programme. With soil temperatures now low enough and sufficient moisture in the ground, we’re looking to get a really good rotational hit of brome and ryegrass as well as black-grass.

Oilseed rape root as well as top growth has generally been good this autumn. However, soil issues left over from last year have definitely restricted rooting in some fields. Wherever this has been the case we’ve been including Nutriphyte PGA or Quark in the spray programme to promote root development. And we’ll continue doing so in the spring. I can’t emphasise enough how important the best possible rooting is for crop performance and resilience, not to mention standing ability.

Recent tissue tests from crops causing us some early concerns have been very revealing, especially where overlaid with soil analyses. They’ve shown us that key areas to watch for this season are magnesium, sulphur and potash as well as the ‘usual suspects’ of boron, zinc and manganese. So much so that, in some cases, we’ve already been going in with prescription foliar nutrients even in the absence of other spraying needs.

Continuing to keep a close eye on the overall nutrient balance of individual crops will be a particular priority – alongside N Min and GAI assessments – as we move into the spring. Wherever possible, we’re keeping as much fertiliser flexibility as we can with straight nitrogen on the one hand and polysulphate or kieserite as sulphur sources on the other so we can best balance the N needs of different crops for the canopy with early S demand.