Arable
Timing is everything for good spring crop management
IN THE FIELD
A mild winter means higher disease pressure on many crops this spring, writes Richard Overthrow
greened up nicely following the fi rst nitrogen doses – after unu- sually pleasant weather in Feb- ruary paved the way for a consid- erable amount of spring drilling and top dressing. Winter rape crops will have re- ceived their fi nal nitrogen doses by now. But some crops were so badly damaged by cabbage stem fl ea beetle they may still be on probation with inputs and ex- penditure still restricted. As soils dry out, later applica-
M
tions are at risk. But once pods form, then liquid foliar nitrogen can be applied to top up the nitro- gen total if a miraculous recovery occurs and you feel the crop justi- fi es a further application.
any spring crops have established well and winter
crops have
Rape in flower With most rape crops well into fl ower now, any opportunity for growth regulation has passed. Backward, late developing crops may still be within the optimum window but these crops are very unlikely to justify any such treat- ment.
Flowering fungicides will be applied soon if not already. We ha- ven’t suffered any serious sclero- tinia outbreaks for some time now but this fungicide timing should still be considered routine, ap- plied early-mid fl ower. Second sprays following up at
late fl owering should only be con- sidered where disease pressure is known to be high. This very dif- fi cult to predict with sclerotinia but should be based on cropping history and previous experience. Any spring cereals still to be sown – or sown in late March – should have all their nitrogen applied either at or soon after drilling. Any second doses on the earlier sown crops should also be applied soon. For later spring cereal drill-
ing, a slight upward tweak in seed rate will also be necessary, if possible.
Disease pressure
This month should see com- pletion of early fungicides and growth regulators going on to winter wheat and barley. Disease pressure is higher this spring due
mainly to a very different winter compared to last season. In early developing wheat
crops, leaf 4 emergence (T0) may arrive in late March but for most crops it’s an early April timing. Leaf 3 is likely to emerge around three weeks later when T1 fungi- cides will be due.
In the eastern region, T0
sprays on wheat should be based on chlorothalonil with triazole, the chlorothalonil will handle septoria but most crops are at risk from yellow rust, hence the need for a triazole (or strobilurin) also. The wheat T1 (Leaf 3) fun- gicide should be SDHI-based though with a resistant variety, later drilling from October on- wards and a relaxed attitude to risk means older chemistry such as triazole plus chlorothalonil can be considered, although robust doses of each are advised. Where eyespot is targeted, Tracker is still very effective but
Timely tips
• Apply fl owering fungicides on oilseed rape
• Apply nitrogen when drilling spring cereals
• Increase seed rate for later spring drilling
• Complete early fungicides on winter wheat
• Apply growth regulators to winter oats
it will need support from other ac- tives if septoria pressure is high.
Winter barley In winter barley, the T1 is usual- ly timed around GS31, typically early April. SDHI-based products are the standard now for this crop with higher doses at this timing than at T2 since the contribution to yield from the lower leaves is greater than in wheat. Growth regulators, in the
form of chlormequat or trinexa- pac products, will also be due on winter oat crops this month, usu- ally between GS31 and 32. Nitrogen programmes on win- ter wheat and barley should be completed this month, particu- larly with many fi rst doses go- ing on early. Depending on devel- opment, later sown wheat crops could wait until early May. Any late doses for protein in wheat won’t be needed until next month. Spring cereal crops are more advanced than in recent years and these earlier sowings may be ready for their fi rst fungicides at the end of the month (GS30-31). Irrespective of sowing date the crop does not respond to high in- put at this timing so don’t spend too much. › Richard Overthrow is a region- al agronomist with NIAB TAG, the UK’s largest independent agrono- my organisation with several re- search centres in East Anglia. For more details, call 01223 342495.
Nitrogen
programmes on winter wheat and barley should be completed.
APRIL 2019 • ANGLIA FARMER 13
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