Last month's Horticultural Development Company (HDC) technical seminar on manipulating the light spectrum for horticulture highlighted numerous ways in which crop growing can benefit, but also illustrated that it is still very much an evolving technology.
The event took place at North Yorkshire's Stockbridge Technology Centre, where the LED4Crops research unit was opened earlier this year.
Dr Phillip Davis explained that his role as HDC-funded "lighting fellow" at the new facility will mean reviewing existing research and practice, developing lighting "recipes" for specific horticultural uses, and in the longer term developing new commercial applications for LED technology.
HDC research manager Dr Debbie Wilson outlined the range of grower-funded work already undertaken on plant responses to light filters. Among findings, specialist UV-O and Luminance films were found to yield increases in plant mass of herbs, but results were dependent on species. UV-O also appeared to reduce infestation of peach potato aphid on iceberg lettuce. One clear conclusion is that different films are suited to different jobs, she said.
Nigel Paul, professor of plant science at Lancaster University, pointed out that the role of light in plant defence is complex, but that UV-C light in particular has a promising role in inculcating disease resistance.
Scottish Agricultural College PhD student Kevin McCormack said results of experiments on using LEDs to enhance the effect of insect sticky traps were so far mixed but blue LEDs showed more promise.
LED-based "plant factories" are already operating commercially in Japan, according to University of Warwick deputy head of life sciences Professor Brian Thomas, rounding up a recent international symposium on the technology in the Netherlands. Dutch growers also report higher tomato yields and reduced Botrytis infestation under diffuse glass, he added.
Lincolnshire Herbs managing director Patrick Bastow said collaboration with European partners is helping his firm to find LED-based alternatives to high-pressure sodium lighting. "It's not all about energy reduction. Crop speeds can be improved too," he said. "But the distribution and mix of LED spectrums is critical and each crop needs a different recipe."
On the economics of the technology, Farm Energy Centre commercial director Chris Plackett said: "LEDs for horticulture are exciting but still in their infancy and currently too expensive for most applications. But the technology is developing fast and prices will fall."
Smart light system
US technology firm Nano Labs has released an LED-based "intelligent illumination system" for glasshouse horticulture. It modifies light output to suit the crop's needs at a given stage of development and uses pulsed rather than continuous light to further reduce energy use.