Plant Records: The ever thirsty sugarcane

You might like a drink at Christmas, but Jenna Loiseau finds that sugarcane is REALLY thirsty.
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By Rufino Uribe (caña de azúcar) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
Name: Sugarcane
Scientific name: Saccarum officinarum
Known for: providing us with sugar and bioethanol
Record broken: being more water-thirsty than soybean or maize

When was the last time you had sugarcane? What if I told you that you eat it almost every day? Sugarcane produces 75% of the world’s sugar, and whenever you eat something sweet, it likely came from sugarcane. Following the demand in green energy, sugarcane has also become a major sugar source for bioethanol production. This makes it an economically valuable crop.

Sugarcane in numbers

Sugarcane originated about 8000 years BC in New Guinea and Asia. It then migrated to the West, where it has been largely domesticated since. Its ability to accumulate sugar in high concentration makes it a valuable crop in nowadays’ society. In 2016-17, it globally produced around 55 million metric tonnes of sugar, which is the weight of 5500 Eiffel Towers. In addition, it yielded 26 million m3 of alcohol, which could roughly fill 9000 Olympic pools. Refined sugar is one of the final products used from sugarcane juice extraction. It is added to many food products you eat every day, from your favourite flavoured latte to ketchup. Sugarcane is a water-demanding crop, making it one of the crops with the highest water requirement.

Why does sugarcane need so much water?

To calculate a crop’s water requirement, we look at several factors: the growing period, the evaporation and the transpiration. Sugarcane grows slowly. Did you know that it takes 18-24 months for this crop to reach maturity, depending on the climate?

Second, sugarcane likes it hot! Optimum conditions for high sugar accumulation are sunny weather with temperatures of around 27 °C. If you prefer similar conditions, surely you wouldn’t mind an extra glass of water when you relax in the sunshine. Indeed, those warm conditions lead to high water evaporation and transpiration. This means that sugarcane is growing in an environment that makes it prone to water loss. For those reasons, it needs about 1500-2500 mm of water throughout its growing period! That’s three times more water than soybean or maize need before they are being harvested.

It’s not just about the rain…

If you were a sugarcane, where would you feel most comfortable? Brazil offers great climate to grow sugarcane at great yield. It is the largest producer with 666 million metric tonnes of sugarcane and 40 million metric tonnes of sugar (2016-17). India is the second producer, with 27 million metric tonnes of sugar. You might think that rainfall in regions like Brazil or India would palliate with the high-water requirement of sugarcane. But, remember that water loss generated by evaporation is a major concern in those regions, and leads to crop losses.

Solutions exist to counteract water losses in those regions. We can improve water efficiency infrastructures like irrigation systems. These systems are already in use on sugarcane farms, and are a great option to optimise sugarcane yields so far. What can science do about this? We can use biotechnology tools to engineer drought-stress tolerant varieties. This would even allow us to grow sugarcane in a water-limited environment. Or, if you would like to contribute yourself, I challenge you to go sugar-free for a week!

References

Dr Jenna Loiseau
Dr Jenna Loiseau

Jenna Loiseau gained her PhD in Biosciences at The Sainsbury Laboratory, where she studied plant-microbes interaction. She decided to study plant science, as she comes from a farming background, and has a keen interest in Food Security. You can follow her on Twitter @loiseaujenna or read her blog sciencewithjenna.


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  • Water is indeed a major requirement fro sugar cane, despite the often held view that plants with C4 photosynthesis, (of which sugar cane is one) are `drought resistant’. This piece emphasise the need for water. But it is far too optimistic in assuming that “We can use biotechnology tools to engineer drought-stress tolerant varieties. This would even allow us to grow sugarcane in a water-limited environment”. The evidence that this will be possible is discredited. It is not a good idea to raise false hopes of overcoming a very complex and difficult problem, not just for sugar cane but for all other crops. . .

  • It would be interesting to compare the water use to the sugar beets that we have in the US. A lot of foodies want to use cane instead of our beets because the beets are GMO. But if they were better on water maybe people would have another helpful data point for comparison.