A single year of oilseed rape may not be a sufficient break to
adequately safeguard first wheats from take-all, reveal the latest
trials at Masstock Arable’s SMART Farm in Wellington, Somerset.
Over the past month serious patches of whiteheads have become
apparent in all six feed wheat varieties in the field-scale trials
drilled in late September following OSR after a previous wheat.
And root inspections have pinpointed take-all as the primary cause.
“Take-all is a fact of life in many of our second wheats
around here,” comments agronomist, Kevin Ashford of Agrownomics
responsible for the farm. “So we routinely use the specialist
seed treatment, Latitude (sithiofam) to keep it at bay.
“If the current trial had been after set aside we might have been tempted
to treat the seed, especially as the land had suffered badly from take-all
in the past. But, as a first wheat after rape, we decided not to.
“All varieties established and developed well and, in view
of the high residual nitrogen levels from past poultry manure applications,
only needed 80 units of N as a liquid in May,” he reports. “We
saw no stunting or other evidence of compromised rooting whatsoever. Until
the middle of June, that was, when the hot dry weather started
to take its toll and substantial patches of whiteheads developed
throughout the crop.
“We found some sharp eyespot on the stems, but no true eyespot;
and the lesions certainly weren’t serious. However, when
we dug up plants and found the classic blackened roots it became
obvious that take-all was the main culprit.”
This evidence reinforces Kevin Ashford’s view that many growers
need to have a better cereal break than just a single oilseed rape
if they are to avoid the scourge of take-all. Especially so if
they sow first wheats in September and their cereal volunteer control
in OSR is not as good as it could be.
“Don’t think you can safely replace second wheat with
rape then go straight back into wheat without taking adequate precautions
against take-all,” he stresses. “You may get away with
it if you drill your first wheat late enough and have plenty of
summer moisture. But if you’ve had take-all problems in the
past you really need to take care.
“The first problem is you probably won’t have the time between
wheat harvesting and rape sowing to adequately control the cereal volunteers
that so effectively carry the disease over. So you’ll have to make sure
you do so in the crop.
“At the same time, you may need a two-year break to clear take-all effectively
from the soil,” adds Kevin Ashford. “Which means specialist seed
treatment could well be advisable – for September-sown crops at least.
“The cost of Latitude treatment may be off-putting if you’re drilling
at1.5 cwt/acre, but if you drill early with a precision rate in seeds/m2 based
on 1000 grain weight you may only need 0.75 cwt/acre so you’ve halved
the treatment cost as well as saved on your seed bill.
“If your rape stubble hygiene is not all it could be and you feel you
can’t justify the cost of a take-all seed treatment, of course, you’d
be better off giving yourself a two-year cereal break by adding peas or beans
to the rotation. Or looking to maize or grass if you’re on a mixed farm
“In any event, do also think seriously about stem canker
and other oilseed rape diseases if you’re considering the
wheat/rape/wheat/rape rotations being advocated by some,” he
concludes. “Our experience shows there are serious dangers
of compromising OSR as well as cereal performance by tightening
rotations too far.”
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