Wheat yields showing increased variability

Farmers have seen greater variability in winter wheat yields over the past decade than they did in the previous five years, according to analysis by Strutt & Parker.

The business, which tracks crop performance through its annual harvest survey, has identified that while average winter wheat yields have slowly climbed since its survey began 19 years ago, growers are now seeing a wider range in yields from year to year.

George Badger, farming consultant and agronomist in the Cambridge office, said: “Up until 2008 you can see that yields were relatively consistent year on year, but afterwards the variability seems to be a lot higher.

“Whilst the low of 2012 and the highs of 2014 and 2015 are a lot to do with the fortunes of rainfall and sunshine, we think there is another factor at play.

“Our survey data, which this year covers 58,000ha, is largely gathered from farms in the East of England and the Midlands where blackgrass is an issue. It is our belief that part of the explanation is a shift to later drilling, as part of a strategy to tackle blackgrass once resistance to contact post-emergence herbicides became more evident from 2010 onwards.

“Late drilling is an essential grass weed management tool, but it does result in smaller root structures which leave crops more vulnerable to weather extremes than they were when people could reliably drill in September.”

Mr Badger stressed that delayed drilling (after 15 October) remained the right course of action on the worst-affected fields, as it gave growers the best chance of both cultural and chemical weed control.

But the data showed how important it was for farmers to make their decision on a field-by-field, rather than whole-farm, basis so that drilling takes place earlier in those fields suited to it.

The most important factor in determining control with pre-or post-emergence residual sprays was access to

moisture, so getting the benefits of autumn rainfall was critical, he said.

An earlier-drilled crop, treated with a well-timed pre-emergence application when there is moisture available, could be better than a later-drilled crop with a pre-emergence application which remains dry in poorer seedbed conditions. Attention to detail is crucial.

“In 2017, people who late-drilled second wheats were caught by the dry conditions and lost secondary tillers to the spring drought. This meant that crops of 6 to 7t/ha were quite common in the survey.”

2017 Harvest Survey Results

According to provisional results of the Harvest 2017 survey, the most significant change in crop performance was seen in winter oilseed rape yields which rose 27%, from a disappointing 2.9t/ha in 2016 to 3.7t/ha in 2017.

“Part of the reason for the improved yields is that only those crops with good potential were taken through to harvest,” said Mr Badger. “In the eastern region, a large area was lost shortly after establishment due to the dry conditions, with Cabbage Stem Flea Beetle (CSFB) damage a secondary problem. Our estimate is that about 80% of the crop was lost in Essex at that point.

“However, elsewhere CSFB larvae pressure seemed to be lower and the OSR plants benefited from higher June sunshine hours than we saw in 2016. This helped to push yields to 6% above the five-year average.”

The overall winter wheat yield for 2017 was 9.1t/ha, which was up 2% on the previous year’s average of 8.9t/ha.

The increase was largely attributable to the better performance of first wheats which yielded an average of nearly 9.5t/ha, compared to 9.2t/ha in 2016. In contrast, second wheats came under more pressure and averaged 7.8t/ha, compared to nearly 8.8t/ha last year.

“It was a mixed year for wheat,” said Mr Badger. “The open autumn in 2016, with rainfall levels in the Cambridge area of only 20mm, compared to the five-year average of 57mm, encouraged growers to drill later.

“However, crops did not tiller proficiently during the cooler months and didn’t get the duration of growth they needed in the spring to compensate. Lodging was also a problem for many growers, with rains in May and June encouraging late nitrogen uptake and a surge in growth. The wet July and August also hit Hagberg levels and specific weights.”

Reflecting the challenging year for spring crops, because of the lack of rainfall in April, spring barley yields were down 7% on last year’s levels to just under 6.0t/ha. Lodging was an issue in a number of crops, as was brackling, which led to high harvest losses as not all the crop could be picked up.

Spring beans also struggled in the dry conditions with yields averaging 3.8t/ha. “For the first time in the history of our survey, winter beans averaged significantly higher than spring beans,” said Mr Badger.

“The open autumn offered the right sort of establishment conditions for winter beans. In contrast, spring beans struggled to develop decent root structures and high temperatures during flowering also affected pod set.”

There was better news for growers of winter barley, who saw yields rise 9% to average 7.3t/ha. This was up on DEFRA’s estimate of 7.1t/ha, but below the S&P five-year average.