Wheat eating into jowar farming, trend ill-suited to rising heat, says study
Mumbai: Since 2000, area under wheat production in India has grown 17%, driven in part by expansion of production from the traditional breadbasket of the northwest towards the central semi-arid parts of the country. In the same period, and in much of the same semi-arid areas, land under jowar or sorghum cultivation fell by 21%.
This trend is unsuitable amid rising global temperatures, suggests a new study comparing climate sensitivity of the two crops. Rising temperatures could reduce wheat yields in India by 5% by 2040 and by 10% by 2050, the study found, assuming no mitigating interventions. By contrast, increased temperatures had little effect on jowar productivity, researchers found.
The study found total water requirement for wheat could increase by 9% by 2030, compared with a 6% increase for jowar, in a higher warming scenario. “On balance, sorghum provides a climate-resilient alternative to wheat for expansion in rabi cereals,” said Ruth DeFries, study lead author and professor of ecology and sustainable development in Columbia University in New York. She added, “However, yields need to increase to make sorghum competitive for farmers.”
Jowar, or sorghum, is known as the “camel of crops” for its ability to grow in dry conditions. It consumes 1.4 times less water than wheat. On the other hand, wheat’s high yields mean more crop per drop—water used per tonne of wheat, or the “water footprint”, is about 15% lower than jowar. But even that advantage could erode in the future. DeFries and others found a 12% increase in the “water footprint” of wheat by around 2050, compared with a 4% increase for jowar.
What makes wheat especially vulnerable to rising temperatures is that its growing season extends into summer. Wheat is thus more exposed to heatwaves, which are expected to become more frequent.
Last February, an early and record-breaking heatwave scorched wheat harvests and led to restrictions on exports, at a time of supply disruptions caused by the war in Ukraine. India is the world’s second-largest producer of wheat. The event spurred DeFries to undertake this study.
Looking at the data, she found that total wheat production in India rose by 42% between 1998-2002 and 2012-17, driven by increases in crop area and yield, which went up by 17% and 26% respectively. Meanwhile, production of jowar declined 5%, despite a 37% increase in yield. The decline was driven by a 21% reduction in crop area.
The area trends were driven by the semi-arid central region, where both jowar and wheat are grown, but wheat production has been expanding. Yields for both cereals has increased in these areas since 2000, but wheat yields remained higher and almost double that of jowar, researchers found. “One of the reasons why the jowar yields are lower is because it hasn’t gotten the same research attention, the same improvements in varieties that wheat has had,” said DeFries.
That could change with millets in the spotlight now. The UN declared 2023 as the International Year of the Millets, and the government has undertaken programs to boost its production and marketing. Much of the new attention has been on kharif or monsoon millets such as ragi and bajra, said DeFries.
For the study, published in Nature Scientific Reports, researchers used yield models to predict the sensitivity of the grains to rising maximum daily temperatures and precipitation under higher warming scenarios. The study predictions do not take into account mitigating factors such as better crop management or new adaptive technologies.
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