Glasshouse technology: Helping hands

Advances in LEDs, plant monitoring and even robotics will allow growers to improve their production processes, Claire Shaddick finds.

Tomatoes: light level adjusted to optimise conditions - image: Claire Shaddick
Tomatoes: light level adjusted to optimise conditions - image: Claire Shaddick

Much of the talk in glasshouse technology at present is centred on LEDs. They may have been around for decades but they are now finding more applications, such as horticultural lighting, as manufacturers make new advances.

LEDs emit light in narrow band widths, which means that modules can be matched to wavelengths such as red or far-red that, in horticulture, can trigger different plant responses.

As well as offering the advantage of a tailored light spectrum, LEDs have a long life and fast response time and generate less heat than conventional lamps so they can be sited closer to the plant in what is described as "interlighting" between rows.

The basic requirement for tomato production, for instance, has been identified in terms of what is needed from a combination of LED and high-pressure sodium lamps. But the exact "recipes" to match a nursery's priorities, such as more or earlier production or more efficient use of space, have still to be pinned down.

"At the moment, Philips' research module allows adjustment in light levels to experiment with the crop and find the right recipe," says Ross Hibbs, managing director at CambridgeHOK, Philips Lighting's first LED partner for horticulture in the UK. Some scientists believe that LEDs could have a role in prompting specific growth responses at certain points in a crop cycle, such as in the germination of seed or rooting of cuttings.

"The biggest challenge is for growers to understand what LEDs can do for their business," says FEC commercial director Chris Plackett. "Much is still unknown about their capabilities and how different crops will respond - and the price has to be right. Some advantages of LEDs in the future will be in areas that most growers don't even realise. For example, trials suggest that LEDs may help with flavour enhancement of certain crops and also with resistance to certain pests and diseases."

Environmental control

Smartphone apps are entering the horticultural arena, thanks to Hoogendoorn. Its first, the drain notification app, which will be released later this year, connects to the company's iSii climate control computer and can alert growers of hydroponic crops by text message if drain water volumes reach too high a level.

Another big area of development has been how plant responses relate to changes in the glasshouse environment. Being able to collect high-resolution pictures of their crop - whether next to their office or on another continent - and link them to climate control graphs can give growers new insights into their plants' behaviour, says Hortimax product manager Joost Veenman.

With the Hortimax system CropView, developed for its Synopta software, a static camera captures images of a representative area of the crop every 10 minutes day and night. The images - current and from the previous four years - can be downloaded and viewed with graphs of, for instance, temperature or irrigation for the same period.

"It's the grower's job to know what their plants are doing," says Veenman. "But they can't be in the glasshouse all day every day, especially if they have several sites or even sites in different countries. CropView allows them to keep a close eye on their crop's development."

A more recent innovation from Hortimax has been the ability to display temperature measurements as a thermogram - a pictorial representation of temperature at different points in the glasshouse so hot and cold spots can be seen at a glance. "That helps you to decide whether to open or close the vents, for instance, or whether you need to open or close the screens," says Veenman.

Priva is in the final stages of trials with TopCrop, which allows growers to take crop activity, measured as plant transpiration, into account when controlling the glasshouse environment by its Connext computer. Priva says the innovation lies in the combination of measurements at the plant and its immediate vicinity, together with the control system's short response time.

"It will give growers a more accurate analysis of the state of the plant so they can react more quickly to its needs," says Priva UK commercial director Nick Field. "It's already performing well with tomato crops and is expected to do the same with strawberries." The commercial launch is planned for later this year.

Sensors, or electronic noses that can detect pest attack or disease infestation before signs become visible by the chemical signature released by a plant, are attracting research interest. Work at Lancaster University, funded by the Horticultural Development Company, found that so-called "e-noses" could pick up and distinguish between plants under attack from a caterpillar, mite or mildew. The practicalities of using such sensors are now being tested in an EU project.

Time for robots

At one time, robotics was something that only industries such as car manufacturing could afford. But as the cost of the technology has come down, so robots are beginning to find a place in horticulture for automating simple repetitive tasks in the packhouse. Lincolnshire Herbs has recently installed robotics for sleeving pots.

But it is the labour-intensive task of harvesting that, if assisted by robots, could revolutionise the economics of producing high-value crops such as tomatoes and cucumbers on a large scale.

With Dutch growers historically having to pay higher wages than much of the rest of Europe, the Dutch government has already supported research at Wageningen UR to develop a prototype harvest robot for cucumbers. The EU, too, is investing in the CROPS project, which is looking at the development of sensors, robot arms, grippers and intelligence for various tasks in horticultural crops and forestry.

The project is being co-ordinated by Wageningen, which is working specifically on a harvest robot for sweet peppers. "We chose peppers because, after tomatoes, it is the largest fruit vegetable crop in the Netherlands and there has hardly been any research," says coordinator Dr Jan Bontsema, a senior scientist at Wageningen.

The design objectives and working principles for a harvesting robot have been identified and preliminary results obtained on sensing to distinguish between fruits, stems, leaves and peduncles and to be able to view fruits from different angles.

"The University of Munich has built the first prototype of the manipulator, which will be tested in practice in the Netherlands at the beginning of April," says Bontsema. "We hope that by the end of the project, in 2014, we will have enough results for the industry to manufacture a commercial robot."

Focus on energy saving

Ways to cut heating bills are never far from the minds of growers of protected crops. "Many are very focused on energy saving, some by adapting older methods such as combined heat and power or crop screens," says FEC Services commercial director Chris Plackett.

Double screening is taking off and Lincolnshire Herbs is already using the technique. "It is saving five to 10 per cent on heating bills and we're already thinking of extending it throughout the glasshouse for 2012-13," says managing director Patrick Bastow.

The company is also looking at a geothermal heat pump. "It offers benefits in energy saving and helping to reduce our carbon footprint, which is vital given supermarkets' and public demands," he says.

A recent project by FEC, funded by the Horticultural Development Company (HDC), suggests that for nurseries with access to low-grade heat such as a ground source heat pump, a ducted air system, where air is drawn by fans through a heat exchanger, could save energy, even allowing for powering the fans. Trials on a tomato nursery found it also increased yield, with less need to vent for humidity control.

A new HDC project is looking at whether fans and ducts installed solely to improve air distribution from a conventional heating system could also have spin-off benefits for saving energy and improving yields.

Lighting of the future

LED lighting could revolutionise the way some crops are grown in future. "Where LEDs will be ideal is in multi-tier systems," says CambridgeHOK managing director Ross Hibbs. "One possibility is half-a-dozen benches on top of each other in a glasshouse with rows of LEDs between."

The use of LEDs could also see some protected cropping or aspects of production move into climate-controlled chambers where all natural light is excluded.

For instance, to speed up plant propagation in winter and improve consistency of plant quality year-round, Dutch hydroponic lettuce grower Deliscious has invested in an 8m-high climate chamber, housing seven tiers of plants lit only by Philips' GreenPower LED modules.

More information will emerge from an initiative at the Stockbridge Technology Centre (STC), expected to start this year. With input from CambridgeHOK, Philips and Lancaster University, STC plans to compare blocks of conventional growing with production in tiers using LEDs both in a glasshouse and in an insulated building where the LEDs are the sole light source.

"The aim is to compare costs," says STC science director Martin McPherson. "In a non-greenhouse structure, if the lighting gives off enough heat for the crop, it's then a question of whether it is cheaper to grow that way or in a glasshouse that is expensive to keep to the right temperature."


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