A few bad days can have a huge affect on winter barley
As the winter barley harvest drags on, reality has dawned of the dependence we have on weather conditions during grain fill in order to maximise yields. As growers and agronomists, over the course of crop cycle all we can do is to provide as many viable grain sites as possible and produce as much green leaf area as possible.
Green leaf produces assimilate which goes into filling these grain sites to complete the circle.
In order to maximise assimilate production, green leaves require bright, cool conditions to work at their best. Whether it was the high temperatures in May, or the low sunlight in June, the grain fill weather conditions encountered by the 2016 winter barley crop was the limiting factor in generating yield.
Winter barley in particular is very susceptible to weather during grain fill, as the grain fill 'season' is so short between the time that the crop goes from flowering to maturity.
So a few days can have a hugely negative effect, like we encountered in 2016, or hugely positive effect, as we saw in 2015.This effect is especially pronounced in the six-row varieties.
Like a sow with too many bonhams in a litter, six-row barley has a huge number of grain sites that need feeding. If conditions are good and there is plenty of 'milk', the overall effect is great as a big number of well-fed bonhams leads to a bumper crop.
However, if milk is limiting, the two or three too many bonhams have a negative effect on the whole litter, not just the extra ones, so every piglet ends up a runt and overall production is below what you would expect from available assimilate.