They think it’s all over….

28 Jun 2014

Until the World Cup it has been a good footballing year for me. As a lifetime supporter of Leicester City, I was over the moon this spring because an amazing unbeaten run culminated in their promotion to the Premiership as champions of the Championship. Not only that, but I watched with a mixture of fear and excitement as the mighty U’s (for the few who do not know – Cambridge United) climbed to the top of the FA Conference Premier League at Christmas and then hung on for second place. A trip to Wembley was necessary to see them grab promotion to the Football League. This was their second Wembley appearance of the season as a few weeks previously, one of my daughters and I also watched them win the FA Vase (the equivalent to the FA Cup for non-league clubs). The photo shows them on their victory parade through the city at the end of the season.

Cambridge United victory parade 2014

Cambridge United victory parade 2014 2








Then came the World Cup; so near and yet so far. Naturally I remember the 1966 World Cup final win over Germany although I did not watch it on TV. Believe it or not, I was playing cricket for the local farmers’ team. However, we did have a radio behind each set of stumps and really lived the drama. In many ways it was perhaps a better experience than watching it on TV.

This got me thinking about how competitive we were in the world wheat yield stakes in 1966. So I looked it up and with increasing excitement found that our average yield that year of 3.86 t/ha was higher than Germany (of course!), Ireland (the current country with the highest average yields), New Zealand and France. At the last moment I thought I should check some other likely candidates and I am afraid that Denmark spoilt the story, with an average yield of 4.27 t/ha. It is sobering that their current yields are being compromised by significant nitrogen restrictions.

There is much current excitement about ‘breaking the yield ceiling’. It’s a bit like the World Cup; we spend hour upon hour planning the strategy and tactics only for the weather to prove too strong an opposition. We get so close but it is either not wet enough in the summer (e.g. 2013) or too wet and dull in the summer (e.g. 2012) for us to claim victory. Sometimes we lose in extra time. 2008 was our record year for average yields and it could have been so much better had it not been for the extremely wet harvest. That year I heard over and over again from farmers who said that they were half-way through harvesting a field when the weather broke and when they recommenced a fortnight later, the yields in the remainder of the field were a tonne/ha less.  As one Essex farmer sagely told me recently, wheat has only to look good once and that is when it is feeding into the combine i.e. it is not over until it is over.

There are some amazingly good looking wheat crops at the moment. With the right combination of sunshine and rain there could possibly be some bumper yields around. The recipe for very high yields is well known, the crop needs to intercept high levels of solar radiation and not run short of moisture. High temperatures during grain fill, particularly around and just after flowering, will reduce the yield potential.

There is a need to maintain a green wheat canopy until the end of grain fill. This is not the same as saying that a green crop canopy should be maintained for as long as possible. There is evidence in scientific literature that clearly shows that the relationship which exists between maintaining a green canopy and yield has a time limit (measured in day degrees) which is around the time of the end of grain fill.  

Extending a significant green canopy beyond that time does not further increase yields. Additionally, it does not have to be a full canopy at the end of grain fill, field experiments carried out at the University of Reading just over ten years ago suggest that by around the end of grain fill the majority of the flag leaf can be senesced and maximum yields can be achieved. Whilst I accept that such a canopy at the end of grain fill could possibly be insufficient for a record yield, it is clear that the canopy needs to be kept green but perhaps the rider ‘for as long as possible’ may be the route to some unnecessary expenditure.

It is interesting to note that whilst barley can be very different to wheat a recent HGCA project report shows that light interception by the canopy of spring barley must only be protected for approximately the first 75% of grain fill in order to maximise yield; a period of three to five weeks from 50% ear emergence depending on the site and year.  After that period, yield is insensitive to major reductions in light interception (e.g. caused by leaf diseases) probably because grain filling can be completed using dry matter from storage reserves.

So please remember, as always, do not get carried away with dogma but look at the results of field experiments and do not try to maintain the green canopy at all costs. Green is not necessarily the new gold.