Monday, July 15, 2019

Timing is everything for good spring crop management

April 1, 2019 by  
Filed under Crops

A mild winter means higher disease pressure on many crops this spring, writes Richard Overthrow.

Many spring crops have established well and winter crops have greened up nicely following the first nitrogen doses – after unusually pleasant weather in February paved the way for a considerable amount of spring drilling and top dressing.

Winter rape crops will have received their final nitrogen doses by now. But some crops were so badly damaged by cabbage stem flea beetle they may still be on probation with inputs and expenditure still restricted.

As soils dry out, later applications are at risk. But once pods form, then liquid foliar nitrogen can be applied to top up the nitrogen total if a miraculous recovery occurs and you feel the crop justifies a further application.

Rape in flower

With most rape crops well into flower 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 treatment.

Flowering fungicides will be applied soon if not already. We haven’t suffered any serious sclerotinia outbreaks for some time now but this fungicide timing should still be considered routine, applied early-mid flower.

Second sprays following up at late flowering should only be considered where disease pressure is known to be high. This very difficult 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 drilling, a slight upward tweak in seed rate will also be necessary, if possible.

Disease pressure

This month should see completion 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 fungicides 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) fungicide should be SDHI-based though with a resistant variety, later drilling from October onwards 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 it will need support from other actives if septoria pressure is high.

Winter barley

In winter barley, the T1 is usually 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 trinexapac products, will also be due on winter oat crops this month, usually between GS31 and 32.

Nitrogen programmes on winter wheat and barley should be completed this month, particularly with many first doses going on early. Depending on development, 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 first fungicides at the end of the month (GS30-31). Irrespective of sowing date the crop does not respond to high input at this timing so don’t spend too much.

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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