Wednesday, July 18, 2018

Timings vital for optimum crop establishment

September 12, 2017 by  
Filed under Crops


Crop management will be particularly important this autumn following a wet harvest, writes Richard Overthrow.

Harvest has been a challenge to say the least. But drier weather eventually allowed it to get into full swing from mid-August. Soils have started to dry although some growers must still be patient with drilling if only to let the land drain a little.

Hopefully, most oilseed rape has been sown and generous moisture levels will at least have helped establishment. Crops coming through will need constant monitoring for slug and flea beetle activity. Aphids arriving before the four-leaf stage will need treating for Turnip Yellows Virus.

Some may still have oilseed rape to put in but for this area we are not late yet. As stressed many times, prompt emergence is essential to combat flea beetle in particular but with reasonable soil moisture this should still be possible even for these later sowings. Seedbed nitrogen will be more important in this respect.

Phoma infection

If establishment is successful, the next issue is possible phoma infection appearing before the end of this month, requiring an early fungicide. There are good prediction models for the arrival of infection but growers should still be guided by disease levels in their own crop.

Early infection is possible and any crops needing treatment before the end of this month will almost certainly need a follow-up treatment later in autumn.

Also, if weed control was delayed to allow assessment of crop establishment, then treatments should be applied soon, the early residual products (metazachlor etc) still work better at pre-emergence of the target weeds.

Continue to monitor volunteer cereals in rape crops, once these reach the two-leaf stage they become particularly competitive and should be removed by then. In particular, lodging and brackling in barley was a common problem this year and combine losses may have been high, leading to high volunteer populations.

Winter cereals will be going in this month though whatever the cereal crop, fields with grass weed problems should be left until the end of the month at least. Only wheat crops going into fields with no grass weed problems, and of varieties with good disease and lodging resistance, should be sown before the middle of September.

Barley potential

Winter barley should be drilled towards the end of this month or early October. Sowing beyond that would reduce the crop’s potential significantly. Any earlier than mid September and the pest and disease pressures on barley increase more than they do in wheat. Oats are more suited to October than September sowing.

For grass weed campaigns, it is always worth stressing the importance of pre-emergence herbicides and the need to use them to their best potential. Most products are susceptible to dry, cloddy (or wet, cloddy) seedbeds so if it takes a few more days to create a good seedbed then hold off and get it right.

There is a close positive correlation between pre-emergence herbicide performance and autumn rainfall so much of it is out of our hands but try and let soil moisture and seedbed quality dictate sowing date where residual herbicide performance is important.

Aphids and BYDV control programmes will need to start this month on the early sown wheat crops. Most crops will probably have Deter seed treatment but where no insecticide seed treatment was used then for the early September sowings the spray programme should start from the two leaf stage of the crop and be repeated as each spray’s efficacy fades until aphid flight ceases, usually in early November.

Even the Deter treatment may need a follow-up spray if mild conditions persist as they did last autumn. For later sown crops a single spray may suffice, applied towards the middle of next month but again additional treatment cannot be ruled out.

Metaldehyde will once again be closely tracked this autumn so growers will need to be careful and accurate with applications, and perhaps consider using ferric phosphate for all treatments. Slugs will need to be monitored carefully in all autumn crops but only treated if damage is seen or slugs are found in bait traps.

Richard Overthrow is a regional agronomist with NIAB TAG, the UK’s largest independent agronomy organisation with several research centres in East Anglia. For more details, call 01223 342495.


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