Moving on up: End of the wheat yield plateau?
With enough of the wheat harvest complete to get a good idea of national yields, there is growing evidence that the ‘yield plateau’ may have been breached.
UK national wheat yields seemed to stagnate after the mid-1990s, with the UK average yield hovering persistently just around or below 8t/ha. Increasing concern within the industry led AHDB to commission a review in 2011 to try and determine the cause. The review, undertaken by NIAB, examined a wide range of data, including agronomic, economic and environmental data, to try and get to the bottom of the problem.
The ‘yield plateau’ report suggested several factors might be holding back yields, including sub-optimal N and S fertiliser use, soil compaction and a failure to exploit the latest agronomic advances by some farm businesses.
So far, this year’s average wheat yields, according to recent ADAS figures, are 8.1 to 8.2t/ha. These figures are above the five-year average and a clear upward trend is starting to reappear in wheat yields once again. In fact, the five-year rolling average will breach the 8t/ha barrier for the first time – even if this year’s average is just 8.1 t/ha (Figure 1).
Figure 1. UK average wheat yield (X) and five-year moving average yield, with 2017 yield estimated by ADAS at 8.1t/ha (grey) (source: Defra)
What is driving this seeming change in fortunes for wheat yields is unclear, there are probably a number of factors involved. Wheat breeders continue to deliver new varieties with higher yield potential, but what has really changed is many of these varieties now have very good disease resistance profiles, making them more forgiving of poor fungicide timing resulting from weather or other issues. Indeed, evidence from the latest Recommended Lists harvest results shows that varieties at the top of the yield tables are associated with good resistance to septoria tritici.
An increasing number of growers have also started to focus more on soil management – from clearing field drains, to incorporating cover crops in the rotation – while others are starting to get a grip on black-grass control. Improved wheat prices may also have given growers more confidence to invest a little more in the crop.
Will this upward trend continue or is this just a blip? It’s difficult to say. But things are looking hopeful, especially if growers continue to tackle the multiple constraints on yield outlined by the yield plateau report.
The new AHDB Nutrient Management Guide (RB209) gives updated recommendations for N and S fertiliser applications, which provides another way for growers to tailor agronomy better to the needs of modern varieties.
AHDB’s focus on driving advice at a local level, including a greater focus on on-farm trials, should aid growers in accessing the latest independent advice, tailored to their region.
Recent world-record breaking UK wheat yields show what can be achieved when the crop is really pushed and the weather is kind. While 16t/ha may not be possible for all growers, the return of upward yield trends now seems a real possibility. We appear to be heading in the right direction…