Much of the improvement in UK crop yield is due to improved cultivars. In the AGOUEB project, we grew a subset of cultivars representing 25 years of recent breeding history in the same fungicide-treated trial over a 3 year period at 7-8 UK sites each year and estimated a significant rate of breeding progress for yield at over 0.5% per annum. Despite the increase in genetic potential, analysis of official statistics shows that on farm average yield figures appear to have reached a plateau in recent years. The reasons behind this decline have yet to emerge but it is probable that on-farm yields would be in decline without the development of new cultivars.
Samples from the trials were micro-malted in collaboration with member companies of the MAGB and the data showed that there had been a significant increase in malt extract potential for spring barley, even when the analysis was restricted to just those cultivars that had received at least a provisional recommendation for malting use by the Institute of Brewing and Distilling. For winter barley, the scatter of points was considerable meaning that the relationship of malt extract with time was non-significant but it is noticeable that the mean malt extract was some 10 litre°/kg lower than that of the spring crop. This means that the spirit yield per tonne of malt used is likely to be significantly less from the winter crop compared to the spring as there was no significant relationship of the fermentability of malt extract over the time period surveyed nor any significant difference between the crop types for this character. Taken together, there has been an overall improvement in the predicted spirit production per tonne of malt from 1991 to 2013 (Bringhurst, 2015). Whilst the grain nitrogen content of both crop types has decreased significantly over the period, there were few significant trends amongst other malting quality parameters. There has been a significant decrease in wort viscosity in winter barley of approximately 0.3 milli-Pascals p.a. but it was still greater than the average viscosity of the spring barley malting cultivars. Whilst the wort β-glucan content has also decreased over the same time-period, the relationship with time was non-significant and so the improvements in this aspect of malt processability are probably not solely due to changes in β-glucan synthesis and degradation potential.