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Crop Advice & Expertise

6 agronomy decisions to make as a new season starts in the west

It’s decision time for oilseed rape in the west. Gareth Bubb looks at the case for and against and other key agronomy decisions this August.

1. Decision time: do you continue to grow oilseed rape?

There has been a lot of debate about the future of oilseed rape on farms. The case against is obvious: cabbage stem flea beetle attacks have made establishment much more challenging and riskier.

This season, I think weather around establishment will dictate for many growers whether they are going to have another go or not bother. If there is an opportunity, oilseed rape does provide a lot of benefits in the rotation so shouldn’t be dismissed easily.

Its earlier establishment and harvest times fit in with other crops, so it can benefit the subsequent crop either by allowing earlier establishment or giving time for a catch crop before wheat, for example. Financially it will also make a good margin, if you can grow it successfully.

The key for oilseed rape is attention to detail and treating it as a crop that will produce a margin. If you can get it in and away, and be willing to adapt to the season that will give the best chance of success. Planting it with the expectation that it will fail, probably means it does just that.

Look for sufficient moisture around drilling and how you can conserve it, use starter fertiliser to help get the crop away, and consider growing a hybrid variety. Our recent CSFB management survey highlighted that hybrid growers were more likely to succeed with oilseed rape, and the extra cost can be mitigated to a certain extent with risk-sharing establishment schemes.

The benefits of hybrids are more likely to be seen in the more iffy situations when it is put under stress, and that’s exactly what we’re seeing with oilseed rape pretty much everywhere at the moment.


2. Don’t be afraid to plough if you need to reset grassweed control

Now is the time to plan weed control tactics for next season. It’s best to be flexible – know what you are trying to achieve, and use the right cultivations for the soil type.

If your grassweed control was particularly poor for whatever reason last season, then you might need to reset and use the plough. Do not be worried if you have invested a lot in your soil structure because one season’s use of the plough doesn’t undo all of that good work. TThere are a lot of studies that suggest that if you have made the effort to improve soil structure, it will be in better place to recover after you have ploughed.

On the other hand if weed control was good and seed return low then don’t cultivate too much as you don’t want to disturb the soil lower down and encourage seeds from depth to come up.


3. Plan catch crops or stubble management to manage fields between crops

Where fields have been harvested sufficiently early it gives a good opportunity to get a catch or cover crop in, which can help improve soil structure and organic matter. Think about what you’re trying to achieve, and how long you’re putting it in for. If it’s ahead of a spring crop what species you choose may well be different to those if it’s only going to be for 1-2 months, and how much you’re going to spend may change.

If you have a weed issue, you don’t want it to be too thick because you want the grassweeds to germinate so you can spray them off with Roundup (glyphosate) ahead of drilling. Species with high biomass, like phacelia or mustard, might smother out any grassweeds, but make good catch crops in other situations where you’re looking for biomass.

Using flying flocks to graze cover crops are a potential extra revenue stream, but make sure you know who is going to be managing them and how. Ideally they need to be managed so they’re moved regularly and don’t damage the soil.

Fields harvested later are unlikely to have time to grow a catch crop ahead of wheat, but good stubble management can help with weed control. For stale seedbeds research suggests that two sprays of Roundup is the optimum, before you start increasing selection pressure.


4. Consider contractors for pre-emergence sprays

When it comes to drilling winter cereals this autumn if you have grassweed issues don’t drill every field before thinking about applying pre-emergence herbicide sprays. If you drill everything and then can’t get on with the pre-emergence on black-grass land, you’re in trouble right from the start.

Try to drill and spray in blocks and if you haven’t got the capacity to do that, then consider getting contractors in.


5. Weigh up pros and cons of earlier drilling

The mindset of a lot of growers in the west, after last season where they didn’t get crops established in the autumn, will be to get cereals in early. It’s a difficult decision, as going early increases potential yield, but also the threat from grassweeds, diseases like Septoria and barley yellow dwarf virus. Delaying reduces those threats but also potential yield and increases the chances of drilling in adverse conditions or not getting it drilled at all.

Only hindsight, unfortunately, tells you what the right thing to do is, so the only thing you can do is think about the pros and cons and balance the risks in your situation.


6. Consider tuber blight activity in potato blight programmes

We’re reaching towards the end of blight programmes, so tuber blight activity becomes important. There are fewer actives available to control tuber compared with foliar blight, so hopefully you have structured your programme to allow these products still to be used. Infinito (propamocarb + fluopicolide) has good activity against both foliar and tuber blight.