A simple, inexpensive trick can boost food production and even make it possible to grow crops in places where they usually don’t grow.
Growers can increase the yield of their crops by covering them with a plastic that increases the amount of red light on the plants. This simple technique could help feed the growing world population – although it remains to be seen whether it affects the taste and nutritional value of the plants.
Red light
We have known for some time that mainly the red part of the sunlight contributes to the growth of plants. This light stimulates the leaves to produce chlorophyll, which is necessary for photosynthesis. Some farms therefore use red LED lights to increase their yield. But the installation of these lamps is expensive, they consume a lot of energy and they do not spread the light on the plants as evenly as sunlight.
ALSO READ
‘In addition to a nitrogen crisis, we have a phosphate crisis’
To address these issues, chemists Alexander Soeriyadi and Alexander Falber of the University of New South Wales in Australia have developed a new material. The stuff, which they call LLEAF, converts the green part of sunlight – which contributes little to plant growth – into red.
It is a transparent plastic with a fluorescent dye that absorbs green wavelengths and gives it back in the form of red. It can be hung over existing greenhouses. As a result, the light inside the greenhouse turns a soft pink. ‘It’s quite beautiful,’ says Soeriyadi.
Pak choi and lettuce
When they put their plastic to the test in the greenhouse, the researchers discovered that it significantly increased the yield of several crops. For example, the production of pak choi increased by 37 percent. “Everyone was very skeptical when we told this, because the greenhouse industry is already optimized so that you normally only get one-digit improvements with new technologies,” says Soeriyadi.
The material is now being tested in larger, independent experiments. These are run by the University of Western Sydney and the New South Wales Government’s Department of Agriculture.
Plant biologist David Tissue of the University of Western Sydney and his colleagues recently did a trial with lettuce. They installed the plastic over a greenhouse so that it covered a 200 square meter plot of lettuce. Next to it was a plot of lettuce that was not covered by the LLEAF plastic.
The yield of cos lettuce increased by 14 percent when the material was used. That of lettuce increased by 27 percent.
‘I think this technique could be very important, especially because it is inexpensive and can be applied to already existing installations,’ says Tissue. He is now testing LLEAF on cucumbers, and plans to test it on several other crops over the next five years.
The Ministry of Agriculture is currently testing the material on blueberries, but the results are not yet available.
Nutritional value
An important question is whether the lack of green light, or the increase in red light, is damaging the plants, Tissue says. The lettuce growing under the plastic took on an orange hue, probably because the red light impacted their biological dyes, such as carotenoids. “We need to do follow-up research to see if this changes the taste or the nutritional value,” he says.
Robert Coe of CSIRO, Australia’s national scientific institute, also points out that it is still unclear how well the technology works for other types of crops, such as grains. “But I think it’s worth investigating,” he says.
Soeriyadi and Falber are developing different colors of plastic to match their material to different crops. They hope that boosting crop yields can help meet growing food demand. It is expected to increase worldwide by 56 percent between 2010 and 2050.
Dutch light
According to Soeriyadi and Falber, with other light colors it is even possible to grow crops in places where they normally do not grow. Other conditions, such as temperature and humidity, must therefore be adjusted.
For example, they recently completed a trial with a Dutch strawberry variety in Indonesia. They showed that they could increase their yield by covering the strawberries with an LLEAF plastic that makes red wavelengths longer – and thus even redder. Thus, it mimics shorter days. ‘We trick the plants into thinking that they feel the same light profile as in the Netherlands’, says Soeriyadi.
If the technology works on a large scale, it can therefore help to limit the import and export of food. Countries can then grow most crops themselves, instead of getting them from abroad, says Soeriyadi. “We believe LLEAF can be part of a more sustainable, productive and efficient future,” he says.