The old saying is you can’t change the weather, but you can change the sails.
However, if you’re a wheat plant in a semi-arid zone, you can’t even do that. The best you can do is try to survive.
As the planet continues to warm, plant survival becomes more of a concern for crops such as wheat that feed so much of our ever-expanding population. Much of that wheat is grown in zones closer to the equator where global warming will be more severe. So we have an expanding human population that’s dependent on a crop that’s becoming increasingly difficult to grow.
With a population of only 24 million, Australia does not account for a big piece of the human pie, and Australians don’t consume much wheat.
However, the country is in a semi-arid zone and it does grow about 32 million tonnes of wheat annually, so wheat plant survival in severe heat is a matter of great concern Down Under.
Australian researchers know they can’t turn down the ovens or make it rain, but if they better understand how heat waves impact wheat, they will be better prepared for whatever the future throws at them.
To assist in this endeavour, they are entering real time field observations into software models that will hopefully help Australian wheat producers deal with rising temperatures.
Their field work documents the impact of heat on soil microbial activity, soil structure, soil moisture, air around the plants and of course the wheat plants themselves. Knowing how all of these factors affect crops might someday help farmers protect their plants against the negative impact of heat waves, according to James Nuttall, a scientist with Australia’s agriculture department.
“Heat waves can greatly reduce wheat yields,” Nuttall explains for the Soil Science Society of America.
“Computer modelling aids in finding strategies to limit the impact of extreme weather and climate change. This can specifically come in handy during the sensitive periods of crop flowering and the grain filling phase.”
Nuttall and his team performed three sets of heat stress studies looking at timing, intensity and duration. They tested how plants responded to a multi-day heat wave and if it affected plants more during their flowering or grain-filling phase. They also studied how water availability during the heat wave affected the wheat.
“We have data from three experiment sets on the response of wheat to a range of acute high-temperature treatments for 35, 37, and 42 C,” he said.
“It includes one day, three days and five days of exposure. Results showed that high temperatures five days before the wheat began to flower reduced the number of wheat kernels on a plant. Also, a high-temperature event while the grain of wheat was growing reduced how big it got.”
Team members developed algorithms they called “heat sum,” which encompassed temperature, duration of that temperature in hours and plant stage at which the stress occurred.
Some of their findings showed that high temperature five days before anthesis reduced kernel numbers and overall grain yield, but individual kernel weight and nitrogen concentration increased. For high temperature after anthesis, grain yield and individual kernel weight decreased, but nitrogen concentration increased. Water availability prior to anthesis helped wheat respond positively to high temperature.
They put all the results together into a computer simulation model, allowing them to predict how broad acre wheat crops in the future will be affected by heat waves of different intensity and duration.
Scientists studying climate change are now delving more deeply into plants’ response to carbon dioxide levels, temperature and rainfall. This crop model allows them to test combinations of these factors on growth and yield.
“These models help find ways to combat heat waves,” Nuttall said.
“Computer models help predict how wheat will react to extreme heat so we can try to prevent negative effects in advance. Such algorithms more broadly contribute to developing strategies for crop adaptation to climate change. The work is valuable because crop models identify possible ways to keep producing the food our planet needs.”