Extreme heat as wheat crops reach the flowering stage can negatively impact on final yields.

This is the clear conclusion from modelling work recently carried out by scientists at Rothamsted Research.

The results of this work complement other research focussing on the impact of extreme weather events on crop performance levels.

Farmers around the world are facing more frequent and intense weather extremes due to climate change.

While drought has long been seen as the main danger to wheat crops, this new study suggests that heatwaves at a key moment in the plant’s life cycle may soon pose an even greater risk. 

Rothamsted’s Dr. Mikhail Semenov, explained: “Flowering is one of the most sensitive stages in wheat development.

"It’s when the plant sets grain, which ultimately determines yield.

The Rothamsted study used advanced climate projections and the Sirius wheat model to estimate how short, intense heat waves and droughts during flowering could affect global wheat yields in the future. 

Sirius is a wheat simulation model that calculates biomass production from intercepted photosynthetically active radiation and grain growth from simple partitioning rules.

The results of the Rothamasted study show a clear shift in risk: drought during flowering currently causes more yield loss than heat.

However, its overall global impact is expected to decline slightly in the future.

Heat stress at flowering

Heat stress during flowering, on the other hand, is projected to become much more damaging.

By 2050, global yield losses linked to extreme heat at flowering could rise by about one-third. By 2090, those losses could increase by more than three-quarters. 

So, while the issue of drought remains important, extreme heat at flowering is set to become a growing challenge for wheat growers worldwide. 

Rothamsted’s Prof. Malcolm Hawkesford, commented: “This kind of modelling studies provide critical information on, and pointers to, the traits we should be breeding for now, ready for predicted future climate conditions.” 

For tillage farmers, a number of issues are becoming apparent 

Looking ahead, they should choose varieties with improved tolerance to heat as well as drought 

Growers should also consider sowing dates and management strategies that reduce the risk of flowering during peak heat periods.

Meanwhile, plant breeders will also need to place greater emphasis on developing wheat varieties that can cope with short bursts of high temperature during flowering.