Drought could cut wheat yields by a quarter in UK

Date:05-27-2011

Rothamsted Research's wheat growth model estimated yields for a crop grown on the site's sandy loam soil would be 7.7t/ha, assuming weather returned to average from 16 May onwards, said Eric Ober, drought tolerance research group leader.

That compared with 10.1t/ha for the same crop under no drought stress. "The model assumed the crop was not nitrogen-limited," said Dr Ober. "If you add a limit based on an estimation of how much of the applied nitrogen has been used, then it would push yields down even further."

Experiments in previous years using covered tunnels to simulate drought stress suggested yield reductions of 14-48%, depending on the deficit developed, he said.

Estimates from growers across the country echo the findings, with some predicting average losses of more than 25%.

Essex grower David Lord said his wheat had already sustained considerable damage and average yields could be as low as 5t/ha on his farm near St Osyth, even if significant rain fell in the next two weeks.

"We lost a lot of tillers as it was dry so early and there are patches on the lighter ground, which are effectively dead. I would say we will get about 0.5t/acre off these," he said.

But crop condition varied significantly over the holding depending largely on soil type, he noted. "The heavy ground looks better and if we get rain it could do about 3t/acre."

In Suffolk, yields had been hit, but heavier ground was still holding up, said Brian Barker, who farms near Westhorpe. "We're on really heavy land and our first wheats can yield about 5t/acre, but I think we are probably down about 1t/acre so far."

Later-drilled second wheat crops on lighter ground were not fairing as well and could drop to 8.6t/ha (3.5t/acre), he noted.

Mr Barker invested in a robust T2 fungicide, but planned to skip the T3. "We only grow feed wheat and haven't applied a T3 for the past couple of years. If it starts to get wet we may need to reconsider, but at the moment I don't think we'll need it."

Worcestershire received significantly more rainfall than eastern counties, with 8mm falling in March and 31mm in mid-May. But yield potential had still been compromised, said Masstock agronomist David Vine.

"I would say 40% of the wheat area will have lost 1.2 to 2t/ha of yield potential. On some very thin soil with no irrigation we could lose 4t/ha.

"The 60% that look OK will still have lost yield potential of 0.5-1t/ha and need rain as soon as possible for grain fill. The rain that came recently has helped, but in many cases has not picked crops up."