At the moment theindustry is still mostlyusing high pressure

sodium lights,” explains DrPhillip Davis of StockbridgeTechnology Centre. “Mostpeople already have them,and once you have them it ischeaper to keep them thanto change. However,anywhere a new installationis going in, people areconsidering LED5.”There are a number ofbenefits to using LEDs,including running costs.Professor in Horticulture andProduct Physiology atWageningen University, LeoMarcelis, recently warnedthat energy consumption isthe least efficient aspect ofthe Dutch horticultural sector,accounting for 10 per cent ofthe country’s gasconsumption.“The problem is the energy

needed for lighting, and lightis the driving force behindplant growth,” explained ProfMarcelis. He and hisresearch team estimate thatusing LEDs could potentiallyachieve energy savings of upto 50 per cent of traditionallighting technologies.“LED5 are cheaper to run,

so depending on how manyhours you use them for, youcan save energy and thatcan give you a paybackdepending on energy costs.However we don’t reallyknow the economics of a lotof these things at themoment,” says Dr Davis. “Aswith all new technologies,LED lighting is still quiteexpensive, and this ispreventing rapid uptake.However, as costs come

down and energy prices goup we will probably see morepeople switching to LEDs.”Professor Marcelis adds that

LEDs ability to change thecolour of the light, theposition of the light source inrelation to the plant, and theintensity of the light, wouldenable lighting to be usedmuch more efficiently,resulting in better plantgrowth and a higher qualityproduct.There are also othermanagement considerationsfor growers using the newtechnology. “When you growplants under LED5 they arequite different to under highpressure sodium lights, sopeople have got to do a bitof learning about how togrow the plants. For exampleon ornamentals they mayneed to review their use ofplant growth regulators.

There is a bit of learning tobe done,” explains Dr Davis.Consequently, there are anumber of small trials of LEDlighting currently underway indifferent horticultural sectors.STC has an indoor LED

facility called LED4CROPSwhich has now been runningfor two years. In that timethe team has experimentedon a wide range ofhorticultural plants. “Indoormulti-tiered growing is areally interesting area,” addsDr Davis. “It is graduallyspreading around the world.There are various projectsaround Chicago and lots inKorea and Japan and we arestarting to see a few pop upin the UK. However, we havevery different economics tothose two countries, sowhether it will beeconomically viable as soonhere remains to be seen.”

STC is also engaged in athree year HDC fundedproject looking at the lightresponses of some thirtydifferent crop species.There has also been a ot of

speculation about tailoringLED light output to differentcrop traits and requirements,but Dr Davis says such finelevels of management arenot necessarily required tobenefit from the newtechnology. “You can dothat, and I think ultimately inanother 20 years time,people will do that. Growersassume that you have totailor the light to the eachcrop, but you don’t have to.After all, we haven’t beendoing that for the last 100years. You can buy lightsnow that will work and willpretty much grow mostplants, especially in aglasshouse where there is

18 • LOHTNG

LED hghtng need not be oveMy compUcatedLight emitting diodes (LEDs) are becoming more common as a light source incommercial greenhouse production, with some studies suggesting the global marketcould be worth around £2,385 million by 2020, but cost issues mean that to datetheir use has mainly been in new-build projects. Richard Crowhurst reports.

Stockbridge Technology Centre’s LED glasshouse for tomato production.

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background sunlight anyway.‘One difficulty in tailoring

light to a specific crop is thatevery variety of crop has aslightly different response. Inthis regard, it might be easierfor growers to use a generalLED light and thenmanipulate the plants usingthe other methods that wealready have, “ he adds.“LEDs will generally improve

the morphology of a cropcompared to sodium lights,but there are some caseswhere they do things youdon’t necessarily want, butgenerally it is better thansodium light. People are verynervous about switching asthey think if they get the lightwrong it will go horriblywrong, but I don’t think that’sthe case most of the time.”So far, the main area where

people are starting toimplement LEDs is in highwire tomato projects whereLED inter-lighting is beinginvestigated. STC currentlyhas a new project comparingtomato production underfour different light treatments:standard sodium lighting,sodium and LED inter-lighting hybrid and twotreatments with both LEDtop and inter-lighting, one of

which also has diffuse glassin the roof.In the trials the inter-lighting

is currently arranged in tworows. The bottom one is atleast three or four leavesbelow the bottom of thecanopy and the second isabout 60 cm above this, butDr Davis stresses that thesecan be changed. “I expect alot of tomato growers willhave LED inter-lighting in thenext few years,” he adds.The recently completed

Sandylands Nursery inEvesham is equipped with ahybrid grow-light systeminstalled by Certhon usingLEDs in combination withSON-T high pressure sodiumlights. The combination ofSON-T exposure (1 05 pmol)and LED inter-lighting (1 10ijmol) assures year-roundproduction, with the cropremaining active duringwinter as well as darksummer days. Electricitycosts are expected to bearound 1 0 per cent lower,while there will also be lessexcessive heat from thelamps, reducing ventilationrequirements and savingfurther energy.Dutch tomato grower

Kwekerij Wim Peters BV,

based in Someren, hasalready installed such ahybrid lighting systemcombining LED inter-lightingand High-intensity discharge(HID) top lighting. He hasused Philips LEDGreenPower inter-lighting forhis top-quality Tasty Tomtomatoes. According toPhilips, two other growers inBelgium and Friesland arealso planning to use thecompany’s LED inter-lightingin tomato crops from thisseason.It’s not just tomato growers

who are looking to utilise thenew technology. Dutchgrower Van der Arend Rosesand light manufacturerValoya have invested in aspecial LED trial which aimsto reduce energy use by 25per cent. The scheme uses a‘hybrid’ combination of SON-T and LED lights, partly toreduce the need foradditional heating. SEETONY - SPRINGAccording to Wageningen

University, which is carryingout the trial, it builds on twosmall-scale field trials of lastwinter. These showed thatthe plants under the hybridspectrum yielded up to 5.3per cent more production (in

kg) at a 30 per centreduction of PAR light, in turnoffering opportunities to saveenergy.There is also considerabledevelopment with pot plantgrowers. PKM, one of thelargest pot plant growers inDenmark is doubling the areaunder Fiona FL 300 Lighting,the Danish company thathas successfully researchedand developed theapplication of LED’s since2005. Closer to home S & AProduce the largestindependent specialiststrawberry grower in the UKhas been successfullyworking with Fiona’s FL300GROW for winterproduction.However, when thinking

about using new technology,it is easy to get carried away.Dr Davis also warns growersnot to forget about theimportance of sunlight andthe effect of the glass itself.“Diffuse glass is a lot moreexpensive than standardglass but it can have somehuge benefits depending onwhat crop you have, “ hepoints out. “I think we willsee much more of this in thenext few years, certainly innorthern Europe.”

The company has expanded tofacilities.

angmere wasestablished in 1988 byManaging Director Dirk

Houweling and today it is stillowned by the Houwelingfamily with Dirk at the helmwhilst his sons Dirk andMarcel run day-to-dayoperations with the nursery’sGeneral Mnager, GerardVonk.

From 7.5 acres in 1989 the, company has expanded to

75 acres of modernglasshouse facilities in 2015

q and is the UK’s largestgrower of peppers.Integrating quality productionwith environmentally-friendlyprocesses, around 65 millionpeppers are grown byTangmere for the country’smajor supermarkets.The company’s last openday was held a decade ago:there was a mixture of bothanticipation and excitementfor the 201 4 event. Theweather for such an

important occasuperb with gbthroughout theContingency plplanned and inhad been rainconditions.“Preparation

of the day is vitWe started onsix months befcsaid Mark KnigLEAF organise

workshop lnfor(ID) for participand Mark KnigbHouweling andAssistant MarkManager, attenHampshire worproved very hein networking vgrowers who h‘walked the coi

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The indoor LED facilityTechnology Centre.

called LED4CROPS at Stockbridge

75 acres of modern