Sunday, September 23, 2018

Seedbeds key to good crop establishment

September 3, 2018 by  
Filed under Crops

Good seedbed preparation is a priority following the long, hot summer, says Richard Overthrow.

An early completion of harvest would normally allow us to get the next set of jobs done ahead of schedule, but the dry summer has kept soils dry and discouraged too much seedbed preparation.

Good seedbeds are essential for many reasons so if you can bear to wait for moisture before working soils it will pay dividends. Some fortunate growers have had enough rain to allow soil working soils but hopefully this won’t mean more early sowing than normal. Later sowing in all crops is becoming a valuable cultural control tool.

Hopefully, some rape has been sown. But delaying drilling into this month can be effective against flea beetle. Crops that are coming through will still need constant monitoring for slug and flea beetle activity, and aphids arriving in the crop before the four-leaf stage will need treating as they could be carrying Turnip Yellows Virus.

If establishment is successful, the next issue is possible phoma infection appearing before the end of this month, requiring an early fungicide. This was the case last autumn and many crops required at least two fungicides before the end of the year as a result.

Follow-up treatments

Any crops needing treatment before the end of this month will almost certainly need a follow-up treatment later in autumn. There are good prediction models for the arrival of phoma infection but growers should still be guided by disease levels in their own crop.

If weed control in rape 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. Low soil moisture will slow these down but the main damage is moisture competition and there may still be precious little of it.

Winter cereals will be going in this month – though whatever the cereal crop, fields with grass weed problems should be left until next month. 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.

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.

As mentioned above, for grass weed campaigns the importance of good seedbeds to pre-emergence herbicides cannot be underestimated. 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 crop sowing date where residual herbicide performance is important.

Early-sown wheat

Aphids and BYDV control programmes will need to start this month on the early-sown wheat crops. Many such crops will have Deter seed treatment – in its last year – but where no insecticide seed treatment is 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. For later sown crops a single spray may suffice, applied towards the middle of next month but again additional treatment cannot be ruled out.

Growers will again need to be careful and accurate with applications of metaldehyde this autumn 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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