Mystery of the slowing rise in crop yields
WITH the start of the harvest not all that far away, the last of the cereal trial open days are drawing to an end.
These events – which can attract grain growers from across the country – are a bit like fashion parades and motor shows for the farming world. Growers get the chance to see what the new varieties of grain coming on to the market look like and how they perform.
Trying to work out if a new variety will be a winner is always a difficult business because a lot depends on yield and quality of the crop at harvest time. However, as in many things in life, it’s not all that unusual for what looks like a front runner to come a bit of a cropper just before reaching the finishing line – in this case when it goes through the combine.
But these crop trials give newcomers, and often the also-rans, of grain varieties a chance to be seen. Rather than being grown in full fields, they are shown off in plots, maybe a couple of metres wide by 10 long.
Most years there are several dozen varieties of each crop type under test – some old favourites, some on the up, some becoming outclassed, some total newcomers. But generally these get thinned out and some older varieties fall into obscurity, some newcomers don’t make it and some become established as big players in the cereal world.
Over the years, breeding new varieties has helped to improve yields, improve resistance to diseases and to encourage different and sought- after qualities in different types of grain aimed at different markets.
But some things have changed. It’s not that long since most farmers would have expected new varieties to come on to the market that would give a 5% improvement in yield over older ones, while at the same time being more disease-resistant or able to cope better with poorer weather.
From about the 1950s through to the later years of the 20th Century, yields probably came close to doubling – partly due to new varieties, partly due to new techniques.
However, I don’t think many farmers would argue with the feeling that in recent years these improvements seem to have been slowing quite markedly. It seems even varieties which look set to give a 1 or 2% improvement in yield in their trial stages never really seem to deliver on this promise on a field scale.
Even the scientists have been noticing that over the past 10 years there has been a levelling- off of growth in crop yields, with few if any long-term improvements.
Various reasons have been put forward, ranging from the ability of crop pests and diseases to find ways round plants’ defence mechanisms or those of the sprays used to control them. The fact that quite a few chemicals have been taken off the market due to tightening regulations, while fewer new ones are being developed, could also be a factor.
Controls and limits on the amount of fertiliser farmers are allowed to use might also be holding back increases and some believe that climate change could be playing a role.
Whatever the cause, scientists are now sufficiently worried to be looking closely at the problem.
With the world population set to hit nine billion by the middle of this century, let’s hope they can quickly find out what’s going against the grain.