Protected crops - LEDs in UK horticulture

LEDs are showing promise in Europe but work is needed in the UK to fill the data gap on their use in horticulture, Hannah Jordan reports.

Cambridge HOK: Philips' UK partner believes LED research needs to develop the right 'recipe' to find which plants use which part of the spectrum - image: Cambridge HOK
Cambridge HOK: Philips' UK partner believes LED research needs to develop the right 'recipe' to find which plants use which part of the spectrum - image: Cambridge HOK

As selected results from various European LED crop trials trickle through the horticulture world, pressure is mounting among the UK's glasshouse growers for more hard data that show the potential benefits of this cutting-edge technology.

Indeed, discussions are now underway at the Horticultural Development Company (HDC) about the possibility of carrying out research later this year that will uncover the financial implications and potential gains of installing LED systems.

Research manager Debbie Wilson says: "We hope to commission some broad work this year that will flush some of the costs involved out into the open that we don't feel are getting out there at the moment through any other means."

Financial viability

Wilson explains that hard facts are difficult to get hold of because LED is still an emerging technology in horticulture. "We have to see whether any of this is going to be financially viable. What is the best way for a UK business to use LED right now?" she asks. "It is a complicated set of data with which to put together a sound business case so what we need is the right information."

Although LEDs are not new, their use in crop production is relatively recent and little detailed research is yet freely available about how plants respond to the light source or the likely financial impact of the systems. They are far more costly than the soon to be phased out tungsten lighting, making their adoption for commercial horticulture a long way from being economically viable.

Last month, on a study trip to the Netherlands organised by the HDC-funded GrowSave project, a group of UK growers saw presentations and practical examples of the Philips LED systems being used on a range of edible and ornamentals crops. Initial results would appear to be encouraging.

Fern producer Vitroplus found that by using the Philips GreenPower LED Production Module it could tier crops in up to 16 layers and achieve more than 50 per cent saving in energy consumption. It also showed improved plant quality and growth speed and a production increase of more than 33 per cent. Strawberry growers, too, reported gains with energy savings of between 82 and 88 per cent compared with conventional methods.

Inter-lighting was another technique showcased on the tour. Because LEDs produce less heat than conventional lamps, growers have found that it is possible to place them much closer to the plants. In the case of roses, lighting deep inside the flower canopy and right next to the stems gives warmth and light to areas that would ordinarily be shaded. In some cases the method is being used as a hybrid system in combination with traditional highpressure sodium lamps (HPS).

GrowSave project manager Chris Plackett says hybrid lighting systems may be the way forward for the immediate future until a lamp is developed that can meet the needs of each application. "LED looks to be a good candidate for night-break and interesting for replacement lighting but it is a bit more limited for supplementary application because some manufacturers don't yet have an offering that gives the complete spectrum needed." Currently, HPS is the standard choice for supplementary lighting, fluorescent for replacement and, until its recent ban, tungsten for night-break application.

Research call

Plackett echoes the call for more research and says it is needed before producers can feel confident to make what will initially be a substantial investment. Growers must get involved in their own trials, he insists. "They must know what they are looking for in terms of the advantage, where they feel their production is lacking. And they need to be on the case now to keep up with information that is coming out of the Netherlands," he maintains.

Lincolnshire Herbs managing director Patrick Bastow, who attended the study tour, says although he is very excited about the potential of LED for his business, he is still to be convinced by some of the trials. "Some of the science we saw didn't stack up because where they are still using HPS as well as LED they are increasing, not decreasing, energy costs. I can't believe that it is the way forward."

Another problem, he points out, is where the LEDs are very close to the flowers, bees are becoming confused or dying when they try to approach to pollinate. Bastow, who has invested in his own trials in Sweden, says the technology and research need further advancement.

"We have a good understanding of what works and what doesn't and our results are very interesting, but we are probably four or five years off making any major investments. Not enough work has been done yet on cost benefit analysis and from our perspective there isn't really a commercial lamp available that can do what we want," he adds.

Consultant Colin Frampton is carrying out smallscale trials on behalf of strawberry grower Hall Hunter. He says it is vital for growers to get involved with their own experiments because until research begins to release hard facts and results into the open, manufacturers are likely to keep their results very close to their chests.

Tim Howarth, who is general manager at Philips' UK partner CambridgeHOK, says developing the right lighting "recipe" is a key aspect to the direction of current LED research.

"We need to know what types of plants are using which part of the spectrum," he explains. "It's about understanding where each species is operating at its optimum so, for example, we know that tomato crops use blue and deep red but strawberries use more of a far red and less of the blue."

Future questions

Potentially, says Howarth, the question in the future will be whether plants can be grown purely with LEDs and no natural light. "If that is the case, can we grow in insulated buildings? Can we reduce energy costs of heating the glasshouses?"

Howarth says there have even been enquiries from growers wanting to grow their crops in hotel basements so they can pick them and take them directly to the kitchens for preparation. "Once we understand exactly what recipe of light is needed this should be possible. The question is, is it cost effective? We are just at the start of that journey."

But Frampton says although it may be a possibility for certain species that require very specific production methods, he is sceptical about growing in natural light-free warehouses. "We have sun for eight months of the year. If you are bottled up in some building with no sunlight and you have to control the air conditioning and lighting all the time, it is hugely costly - surely that's wasting free energy. We could all do with some solid scientific backup so we know the facts," he insists.

Van Den Berg Roses, the Netherlands

Research and development company Plant Dynamics launched a pilot trial in 2010 with Avalanche roses at Van den Berg Roses in Holland.

It combined LED interlighting, where the LED lamps were positioned halfway down the stems among the leaves, with SON-T (sodium) lighting from above. The lamps were kept on for 24 hours. Between December 2010 and July 2011, Van den Berg harvested around 23 per cent more roses.

As a result of increasing the level of lighting by 12 per cent, the number of stems that were produced went up by 22 per cent and the total weight of roses also saw a 17 per cent increase.

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