Late-sown second wheats need effective take-all protection as much as those sown up to mid-October, reveal the latest results from the country's longest running independent trial series.

The 'best practice' second wheat trials conducted since the late 1990s by East Riding Crop Consultancy (ERCC) on two East Yorkshire farms involve around a dozen varieties and up to 15 different foliar treatment regimes each year, drilled from early October through to mid-December, as local conditions permit.

Since its first availability for testing in autumn 2000, the trials have examined the impact of the specialist take-all fungicide silthiofam (Latitude) added to the base seed treatment of
15 of the most widely valued second wheat varieties over a total of 13 years.

Across the whole trial series the response to take-all seed treatment to date has averaged 0.6 t/ha, ranging from 1.4 t/ha in one of the lowest yielding years on the higher risk site to
0.1 t/ha in one of the highest yielding seasons on lower risk ground.

"The average response from crops sown after mid-October was also 0.6 t/ha," reported ERCC's Andrew Beeney. 

"Identical to the response we saw from earlier sowings, this shows good take-all protection is every bit as important for later-sown second wheats. This is mainly because the advantages of less inoculum and lower temperatures are almost invariably offset by the drawbacks of wetter, less well-structured seedbeds and slower root  development.

"We have, however, seen clear differences in the response between the two sites we've used for our trials," he added. "A higher fertility status and lower take-all risk at Beverely has meant an average yield without specialist treatment around 0.5 t/ha higher than our lower fertility/higher risk Coniston site at 8.8 t/ha. This was boosted to 9.1 t/ha with silthiofam – an average response of 0.3 t/ha.

"In contrast, at Coniston we've seen an average 1 t/ha response, boosting yields from 8.3 t/ha  to 9.3 t/ha. Interestingly, therefore, the seed treatment actually allowed the site to out-perform Beverley."

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Treat late or early

The value of treating later as well as earlier sown second wheats is underlined by ERCC  results from the most two most recent seasons. Even though conditions prevented sowing  until mid-November last autumn, the average 2012/13 yield response to take-all treatment at 0.4t/ha was no different from that seen from early October sowing the previous year.

The fact that the bulk of the varieties involved in the work over the years – from Napier in the earliest trials to Grafton, Relay and Tuxedo in the most recent – have been recognised second wheats reinforces the importance of take-all treatment as routine, believes experienced second wheat specialist, David Leaper of Openfield.  As does the trials' emphasis on well-consolidated seedbeds following a plough and power harrow cultivation regime.

"Despite all three key elements of cultural best practice – good second wheat varieties drilled after the end of September into fine, firm seedbeds – with wheat at £150/t ERCC has recorded an average £59/ha return over seed treatment costs," he calculated. "What's more,  the response exceeded the break-even level at this wheat price in 10 of the 13 years. And more than 85% of the 44 separate crops involved showed a positive response to treatment. This is pretty remarkable for any fungicide – let alone with a disease as notoriously variable as take-all.

"Before the advent of take-all specific seed treatment, about the only defence against the disease was to delay second wheat planting until at least mid-October. But this tends to mean less reliable soil conditions and less good establishment. And we know poorer seedbeds and establishment increase the crop's vulnerability to take-all damage. So it's hardly surprising the trials show a similar yield response – albeit from a lower base – from later sowings.

"The lesson is clear," said David Leaper. "Wherever there's a take-all risk, specialist seed treatment is likely to pay dividends no matter how late the drilling.

"This impressive trial series also suggests valuable performance differences between varieties known to be good second wheats that might usefully be exploited alongside the best seed treatment and establishment care to make the very most of the crop."