Saturday, November 28, 2020

Switch to spring crops can help growers avoid autumn risks

December 21, 2017 by  
Filed under Crops

Growers are under appreciating the risks associated with late-autumn drilling of winter wheat – and in some cases would be better moving to spring crops, say experts.

Over the past six years, the average drilling date for winter wheat has moved back by about seven to 10 days, from late September to about 9 October, suggests data gathered by agronomists and crop production advisers ProCam.

This shift reflects the increasing problem posed by problem weeds – such as resistant blackgrass and rye grasses – and the need to kill-off an autumn weed flush before drilling takes place, says Nick Myers, the firm’s head of crop production.

Potential pitfalls

This move is quite understandable, says Mr Myers – although he expresses concern that some growers are failing to consider the potential pitfalls from delaying drilling further into the autumn.

“The loss of yield potential from moving from mid-September to the end of October is relatively small and quite acceptable at about 0.25t/ha on average, but delaying much beyond October can increase yield reductions.”

It can also make grass weed control more problematic if soil and weather conditions deteriorate. “The assumption that conditions will be favourable and that all varieties perform equally well at later drilling dates is rarely true; it is this risk that many fail to consider,” says Mr Myers.

That said, seedbed conditions at drilling are arguably more important than drilling date. Data gathered by ProCam suggests that the best 25% of growers by gross margin are less constrained by the desire to drill on a set date.

“Waiting for conditions to improve is largely a question of nerve. Our data from autumn 2015 suggests the top 25% of growers were less concerned by date whereas the there was a distinct bell curve around early October among the rest. The best growers also spend less on herbicides at £86/ha compared with £101/ha for the rest.”

Seedbed conditions

KWS product development manager John Miles say trials endorse this view. “In a perfect world we would all drilling into excellent seedbeds, but when conditions are against you there comes a point when it is better to wait until the spring,” he says.

It’s a widely supported fact, says Mr Myers. “If autumn herbicides are to work effectively there needs to be greater recognition of the importance of seedbed quality.”

Fine seedbeds ensure even distribution and availability of residual herbicides to germinating weed seedlings. Too many clods and weeds can’t access the herbicide and develop in untreated soil as the clods weather and break down.

Blackgrass control varies according to ground conditions. Success can be enjoyed in a mild autumn and winter but less so in a poor year. Regardless of season though, the risk of poor control increases significantly as conditions deteriorate with the onset of wet weather and falling temperatures.

Variety choice too is important. Often, too few growers think about what characteristics they need in a variety to over-come the problems that arise with delayed drilling.

Vigour important

Autumn and spring vigour is perhaps the most important feature at this stage, but should not come at the expense of grain quality. In this situation, strong tillering varieties such as KWS Crispin and KWS Kerrin out-yield less vigorous varieties, such as Revelation or Skyfall by 6-8%. That is significan.

Data from the AHDB Recommended List supports his point. Of the more popular varieties listed on the list, 12 have a yield performance of less than 100% of controls when sown between mid-November and the end of January.

There are other issues to consider beyond weed control however, such as pest pressures.

“For some growers, late autumn drilling is simply too risky because of wheat bulb fly pressure in some years. In such situations, spring crops are the only alternative,” says Mr Miles.

All commentators advocate keeping to a planned approach when seeking to control blackgrass rather than wavering in the face of favourable conditions that tempt growers to change cropping plans or push-on with autumn drilling.

“In low-pressure scenarios, be flexible with drilling date and focus on seedbed quality. In mid-pressure situations, delay autumn drilling where possible to increase opportunities for good black-grass control.

“In high-pressure situations however, there is little option but to move straight to a spring crop policy.”