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The world is on course to produce more
wheat this year than ever before. Yet as supply rises to meet
demand, so do the carbon emissions from growing and harvesting the
crop.

Now a 25-year long field experiment in Canada shows
that growing wheat can actually take up more carbon than it
releases. Meeting demand for food doesn’t have to mean more carbon
emissions, the study’s lead scientist tells us.

Wheat is in demand

Wheat is the third most-grown cereal crop in the
world, after maize and rice. Demand for
major cereal crops such as wheat is expected to increase by 70
percent by 2050.

In the UK, around two million hectares of land are
used to grow wheat, with the harvested crop worth around £1.2
billion
. But wheat accounts for 30 per cent of emissions from
growing the crops we eat, estimates WWF.

Fuel burned in tractors used to farm land releases
carbon dioxide, as does producing and using fertilisers. These
emissions typically outweigh the amount of carbon dioxide the crops
absorb as they grow.

Now a new study by Canadian researchers, published
in Nature
Communications
, finds that with some changes to farming
practices, growing wheat can actually remove more carbon dioxide
from the atmosphere than it produces.

Little field on a prairie

The US and Canada are the third and fifth
largest
producers of wheat in the world. Between them they
harvested around 90 million tons of wheat last year. Most of this
is grown in the ‘wheat belt’, a vast area of the North American
prairies that stretches across much of central US and Canada.

Map of the wheat belt through the US, which also
extends into Canada. The green shading shows short (light green),
medium (mid green) and tall (dark green) grasses that tend to grow
in the prairies.
Creative Commons

Researchers conducted a field experiment in the Canadian
prairies between 1985 and 2009 looking at different ways to grow
spring wheat. Spring wheat is so-called because the seeds are sown
in the spring, with the crop being harvested at the end of the
following summer.

In Canada and the US, farmers will typically leave a field
‘fallow’, or unplanted, every second or third year to allow water
and nitrogen in the soils to replenish.

But a fallow field must be ploughed regularly to
prevent weeds growing, which uses fuel. More intensive farming
methods, which don’t have a fallow year, often need more
fertilisers and pesticides to keep crop yields high.

In the experiment, the researchers look for ways
to keep wheat yields high but emissions low.

Lentils are the answer

The researchers find that by growing lentils in the seasons
between wheat, more carbon dioxide is stored than emitted,
effectively making wheat’s carbon footprint negative. Overall, for
each hectare of wheat, over 500 kilograms of carbon dioxide is
stored.

So why do lentils make such a difference?
Growing lentils helps replenish nutrients in the soil, which
reduces the need for fertilisers. While not leaving the field
fallow reduces the need for ploughing. Also, by growing crops every
year, they can absorb and store more carbon than if a field is left
unplanted.

The findings show that meeting the growing
demand for food doesn’t have to be at the expense of action on
climate change. As Professor Yantai Gan, lead author of the study,
tells us:

“A large global
challenge has been to meet the need of the increasing human
population for food while reducing the impact of farming on the
environment. This study shows that with a suite of improved farming
practices in crop production, this is definitely possible and
achievable.”

And while the study only looks at wheat in North
America, other nitrogen-loving crops, such as maize and oilseed,
could also reap the benefits in the same way, Gan
concludes.

Gan, Y. et al (2014) Improving farming practices
reduces the carbon footprint of spring wheat production, Nature
Communications, doi:10.1038/ncomms6012

Via: http://www.carbonbrief.org/blog/2014/11/why-feeding-more-people-doesnt-have-to-be-at-the-expense-of-the-climate/