Tuesday, August 15, 2017

Global Warming Could Cause Yield of Sorghum Crops to Drop ‘Substantially’

Chart shows how global warming of 1C to 5C above a 1985-2014 average will impact the yield of sorghum (%). Red shows the results for managed field trials at 11 locations across Kansas while orange shows results for data taken from the National Agricultural Statistics Service (NASS). Error bars show the 95% confidence interval. [Source: Tack et al (2017)] Click to Enlarge.
Rising global temperatures could cause yields of sorghum – a cereal crop known for its resilience to heat stress and drought – to fall substantially, new research finds.

Sorghum is the fifth most economically important cereal in the world and is grown in some of the most arid parts of Africa and South Asia, where it is a staple food for half a billion people.

The new research finds that for every degree of warming above a 1985-2014 average, sorghum crop yields could drop by around 10%.  This suggests the hardy cereal may be more vulnerable to heat stress caused by climate change than previously thought, the authors tell Carbon Brief.

However, the indirect impacts of temperature might actually be a larger driver of future sorghum yield declines, another scientist tells Carbon Brief.  It is likely that environmental factors, such as humidity, will have significant role in crop productivity, he says.

Why is sorghum so hardy?
Sorghum is a tall cereal grain that is grown for food in arid parts of Africa and South Asia, and for animal fodder (and sometimes biofuel) in many developed and developing countries.

According to the UN Food and Agriculture Organization, the US is the world’s largest producer of sorghum, followed by Mexico, Nigeria, Sudan, and India.

Farmers started growing sorghum in north-eastern Africa around 8,000 years ago.  Through thousands of years of selective breeding, the crop has evolved to be more resilient to harsh environmental conditions than other cereals, such as maize and wheat.

Sorghum is particularly hardy in dry conditions because it has large fibrous roots which can reach far down into the earth to extract water.  It has also adjusted its reproductive system to withstand high temperatures.

As a result, sorghum has even been suggested as an alternative crop for wheat and maize farmers facing falling yields due to climate change.

However, the new study, published in the Proceedings of the National Academy of Sciences, suggests that sorghum yields will be severely dented by rises in temperature.
Finding a solution
Whether the impacts of temperature rise on sorghum yields are predominantly direct or indirect, the need to help farmers adapt is still there.

One solution for US farmers might be to grow sorghum in cooler environments, such as the US corn belt, researchers say.

However, similar options are not necessarily available in hotter, drier countries, such as Chad, where sorghum is a staple food for thousands of subsistence farmers.

Instead, scientists will need to hunt for new genes that promote resistance to heat extremes and incorporate them into sorghum breeding programs, say [lead authors Jesse Tack and Krishna Jagadish from Kansas State University]:
“Our particular focus was on the potential to adapt using currently available seed varieties.  We find limited scope in this regard.  However, breeding programs can likely introduce new genetic material from sorghum plants existing in nature in order to boost heat resilience.”
Read more at Global Warming Could Cause Yield of Sorghum Crops to Drop ‘Substantially’

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