Home Posts Tagged "tomato"


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A trial with hybrid lighting (SON-T + LED) at Dutch tomato nursery Gebroeders Koot has yielded good results. The LED lamp used in the trial, which was developed on British soil with Dutch input, offers several advantages. One stand-out benefit is its clever design which makes it easy to integrate into existing SON-T installations.

Yields up by more than nine percent after seven months (weeks 48-26). That was the auspicious outcome of a greenhouse trial at Prominent growers Gebroeders Koot in Poeldijk, the Netherlands, where a tomato crop grown under 150 μmol/m2/sec SON-T grow light was compared with an identical crop supplemented with 58 μmol deep red with a little blue LED light. Geert Koot, who had had no previous experience in growing under grow light, was very impressed. “I hadn’t expected the higher light level to make such a difference,” he says. “That will appeal to a lot of growers. The same goes for the lamp itself, which has a surprisingly simple design. It’s fully interchangeable with SON-T, so it fits seamlessly into an existing system.”
“A lot of thought has gone into the functional design,” cultivation specialist Maarten Klein adds. He and his assistant, Tim Valstar, oversaw the trial, which was run on behalf of the British LED manufacturer Plessey. Klein, who has had a lot of experience with grow light, developed this lamp in collaboration with the technology company.

Smarter design

“Most LED systems are difficult if not impossible to integrate into existing lighting installations,” Klein continues. “Growers looking to switch to hybrid lighting currently have to install a whole new system alongside their existing one, often with extra C profiles. That pushes up the cost and results in more light interception, which causes problems all year round. Plessey Semiconductors in Plymouth wanted to eliminate these problems.”
To test the practical value of the lamp in the greenhouse setting, Klein approached several Dutch nurseries. In addition to Gebroeders Koot, trial setups were installed at nearby alstroemeria and gerbera growers and a pot plant nursery.

Trial setup

Although Gebroeders Koot were not growing tomatoes under artificial lighting, they did have a SON-T system in place in a section that had previously been let to another grower. These 1000W lamps supplied 151 μmol/m2/s extra grow light and, of course, the usual radiated heat. LED lamps were added in one bay, ramping up the artificial light level to 209 μmol.
Tim Valstar assisted with the trial and, together with Geert Koot, took measurements in the trial and reference sections. All the relevant crop and fruit features of the variety grown, Brioso, were recorded, varying from growth rate and stem thickness to leaf size, leaf colour, fruit weight and Brix value.


The plants arrived in the greenhouse in week 46. “That’s later than the usual for an artificially lit Brioso crop – they would usually go in in mid-October – but the lighting period was long enough to get a reliable impression of any differences,” Koot says. “The plants developed well in both light environments. But the plants under the higher light level were that little bit stronger with slightly thicker stems and more dark green leaves.”
Due to the extra vigour, the plants under the hybrid lighting regime held the first trusses for longer and they were harvested a few days later than those in the reference sections. The higher yield potential quickly expressed itself in a higher average fruit weight. To maintain the desired fineness, one fruit more was kept on the truss (11 instead of 10) from the tenth truss onwards, without the plants forfeiting vigour.
Valstar: “After week 26 we stopped taking measurements and were able to take stock.” The harvest under the hybrid lighting regime was 38.32 kg per m2 compared with 35.04 kg under SON-T. That represents an increase in yield of 9.35%. The average fruit weight was also slightly higher than under SON-T, at 39.2 grams compared with 38.8 grams.

Flexible use

The attractive increase in yield can’t be ascribed solely to the higher light levels in the periods when both systems were in use. The SON-T system was switched off and the CHP unit shut down for maintenance at the beginning of week 19, whereas the LED system was used from 4 am to 7 am for a further three weeks.
“The option to only use the LED lamps either end of the lighting season would be an extra benefit,” Klein says. “Those are often the times when you don’t need the radiated heat produced by the SON-T lamps. LEDs have virtually no impact on the climate. You can always switch them on if you need more grow light. And because they are much more energy-efficient than SON-T lamps, you also have more flexibility when it comes to deciding whether to generate the energy yourself with CHP.”

375 and 600W

Klein is keen to point out that the prototype trialled at Gebroeders Koot was developed exclusively for research purposes. But the lamp has since undergone further development and a commercial 375W version was launched at IPM 2017. All the LEDs are now in one bay and the fitting, which has integrated cooling ribs, can be attached directly to the trellis.
The lamp is called Hyperion 1000 because it has a photon flux of 1000 μmol/s. “Because of the higher uptake of deep red light, it’s the equivalent of a 600W SON-T lamp but it uses 40 percent less electricity,” the cultivation specialist says. “The producer has also recently brought out a more powerful 600W version which is the equivalent of a 1000W SON-T lamp.”

Ten years ago

There is a lot of added value in the new lamp, Koot believes. “It’s efficient, it has a broad spectrum, and its clever design makes it easy to incorporate into an existing system. That will appeal to a lot of growers. I’m also quite impressed. But because of my age and the fact that I have no successor in place, I have decided not to invest in any more grow lights now. If this trial had taken place ten years ago, I would almost certainly have gone for them. But we very much enjoyed taking part in the trial.”


A new type of LED lamp produced in the UK is achieving interesting results. The clever design makes the lamp particularly attractive. It can be attached to the trellis without the use of C profiles and can be integrated into existing 600W SON-T systems with standard connectors. A more powerful version equivalent to a 1000W SON-T lamp was brought out earlier this year.

Text and images: Jan van Staalduinen.

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Sufficient oxygen in the root environment is a must for a strong, healthy crop. More oxygen makes the crop stronger and boosts production. That’s the experience of Van der Voort Tomaten in Vierpolders in the west of the Netherlands. They use a water treatment system that keeps the oxygen supply in the slab permanently at the optimum level.

Van der Voort grows mini plum and cocktail tomatoes on eight hectares. Three of the eight hectares are artificially lit. This nursery is its second branch: the company, a member of Prominent, has its main site in ‘s-Gravenzande.
Van der Voort bought the Vierpolders nursery a few years ago. The reservoirs there were already aerated with the Agrona Oxybull water treatment system. “It was part of the setup, so we kept using it,” Joost van der Voort explains. “It was only when the system broke down once that we noticed the difference. The roots stopped getting enough oxygen, the crop became less vital and the tops of the plants no longer looked fresh.”

More growth, higher production

The system works with a series of plates lying on the reservoir floor. Air is pumped through a screen containing numerous small membranes, adding millions of minuscule air bubbles into the water. The system is not a massive investment, but according to Van der Voort it is very effective. “The breakdown made us realise just how much added value it delivers. We started off with three units and recently invested in a fourth one. We have also started using the measurements.”
Agrona director Nadir Laaguili explains the importance of sufficient oxygen. “Research has shown that more oxygen in the root environment results in more growth and higher production. A shortage at the roots always and inevitably limits growth.”

Boost for microorganisms

The maximum concentration is ten milligrams per litre. Anything above that is of no use to the plant because the crop doesn’t know what to do with an oversupply. The water can’t retain a larger volume of oxygen either, hence the upper limit of ten milligrams per litre.
According to Laaguili, a higher concentration also improves nutrient uptake. Oxygen is essential for beneficial aerobic bacteria. “If the grower adds extra oxygen in the greenhouse from the day’s supply, they will notice the effects in the crop,” he says. “The plant will be able to feed itself better and the crop will become more vital and grow better. The useful microorganisms in the medium will also receive a boost. So the whole soil food web is strengthened, and that makes for greater plant resilience.”

More and more naturally

Van der Voort uses the water treatment system in combination with AG-Stim from Agrona. This bio-stimulator nourishes and activates the beneficial bacteria present in the soil, accelerating plant nutrient uptake. A side effect of this product is that organic matter is broken down and converted into inorganic material, so the drip lines stay clean. Laaguili: “The volume is very low, but nonetheless: the inorganic material is nutrition for the plant and it is neatly incorporated into the cycle.”
Van der Voort adds: “We no longer need to use chlorine or hydrogen peroxide treatments. And that’s exactly what we are aiming for: to grow more and more naturally with fewer and fewer chemicals. We always used to use ECA water, or electrochemically active water. But that also didn’t fit in with the concept of growing as naturally as possible, so we stopped using it. And chlorine or hydrogen peroxide are also incompatible with growing in a sustainable, natural way because they kill the soil food web.”

Poor supply

Because AG-Stim accelerates nutrient uptake, the grower can set the EC higher, with beneficial consequences for growth, vitality and production.

The product is a perfect fit for a form of horticulture that is geared towards better quality, says Laaguili. “These days, plants only get the four key elements – nitrogen, phosphate, potassium and calcium – and some trace elements. That’s a very poor supply. And it shows: in terms of nutrients and nutritional value, modern conventionally-grown tomatoes are less healthy than organic ones.”
According to the supplier, the product contains 47 important minerals, including essential amino acids. The improvement in plant strength and quality became apparent at the Westland site, where they stopped using it for a while. Van der Voort: “Almost immediately we started getting reactions from the market: ‘Your tomatoes suddenly don’t taste as good. Have you changed something?’”

Checking measurements

The supplier guarantees an optimum oxygen level of 10 mg per litre, providing the water treatment system runs for at least 12 hours every day. The system can be connected to the climate computer. The oxygen concentration is then measured every five minutes, both in the day’s supply and at the drip lines.
The measurements are displayed in a graph and the grower can see at a glance whether everything is going to plan. Van der Voort again: “The measurements enable you to keep an eye on the system. If they indicate that there is insufficient oxygen, there is clearly something wrong in the system. Then you can go and fix the fault. For example, there could be a blockage somewhere, so you will need to flush the pipes.”

Breaking down dirt

But the risk of a breakdown is quite low, both men say. Pumping millions of air bubbles in the reservoir breaks down dirt particles so they don’t become deposited in the pipes. “That works perfectly,” the grower confirms. “We no longer have to clean the silos.”
He is not the only grower using the Oxybull system. The system is installed at about 40 nurseries in the Netherlands, including other companies affiliated to Prominent, 4Evergreen and Red Star Trading. It is also used by growers in Spain and Canada – countries where the company also has branches – including the big tomato producers NatureFresh and Mucci in Canada and Cualin Quality in Spain.


Sufficient oxygen in the root environment is essential for good growth and high production. A water treatment system adds millions of air bubbles into the water supply, producing an oxygen concentration of 10 mg per litre, right at the saturation limit. Van der Voort Tomaten has achieved good results with this system. They use it in combination with a product that has the added effect of keeping the drip lines clean.

Text and images: Jos Bezemer.

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The Plantalyzer is a unique tool for accurately estimating vine tomato crops. It counts the number of vine tomatoes on the plant in the greenhouse and provides reliable information for an accurate estimate of the harvest.

The system was developed in close collaboration with Wageningen University & Research. It uses special cameras to measure the bottom two to three leaf-free trusses. The system maps the trusses per stem, the number of fruits per truss and the colour of each fruit. The Plantalyzer thus provides insight into numbers and colour stages. Linking this information to practical greenhouse data produces an accurate estimate of the harvest.


The tool is able to measure large areas of tomatoes, counting both quantity and maturity. The system does that tirelessly every day, always in exactly the same way, and works fully automatically.
Stand number: 11.115

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Bio-engineers from the universities of Antwerp and Ghent have developed a new type of fertiliser based on bacteria derived from food industry waste flows.

In the Flemish food production industry quite a lot of fertilisers, like phosphor and nitrogen, are lost. Attempts have already been made to transform this waste into microalgae, which is apparently very useful as an alternative fertiliser. “Although the results were successful, it was 5 to 10 times as expensive as conventional fertiliser. We have now cultivated and mixed three types of safe microbes; primarily aerobic heterotrophic bacteria, purple bacteria and – to a more limited extent – microalgae”, explains researcher Siegfried Vlaeminck.

Pilot project

Professors at the University of Ghent set up a pilot project to test the mixture on several plant varieties, such as ryegrass, petunias, parsley and tomato plants. “We noticed that the microbial fertilisers works just as well as conventional organic fertiliser, and in some cases even better”, says Vlaeminck. “It may be more expensive, but because microalgae also protect crops against disease, we believe that this will be acceptable for the market.”


Now that the researchers have completed the pilot project, they are looking to scale up the experiment. A few hundred thousand tons will be needed to ensure a cost-efficient production and reliable supply, concludes Vlaeminck. Greenyard Foods has already professed an interest in participating in the experiment.

Source: HLN. Photo: Mario Bentvelsen.

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Researchers at the Indian Institute of Technology (IIT) in Hyderabad have succeeded in keeping tomatoes fresh for 30 days using special food packaging material. A team of two members led by Dr Mudrika Khandelwal developed the food packaging material, which is made from bacterial cellulose impregnated with silver nano particles.

The bacterial cellulose is prepared using Gluconacetobacter xylinus bacteria in order to produce semi-crystalline cellulose nano fibres from a standard substance that contained glucose. “We can use every type of fruit juice that is rich in sugar to produce bacterial cellulose”, explains Dr Khandelwal.

Smaller is better

The nano-sized pores in the bacterial cellulosic matrix restrict the growth of nanoparticles, thus controlling their growth. Dr Khandelwal: “We discovered that if the silver nanoparticles are smaller the antimicrobial activity will be greater.”


To measure the exact antibacterial activity of the bacterial cellulose the material was first tested on isolated bacteria and fungi that occur on rotting tomatoes. The test showed that the bacterial cellulose killed 99% of the bacteria up to 72 hours after the test was initiated. What’s even more remarkable in this experiment is that the food packaging material also demonstrated fungus-combating activity.

Retarding the aging process

Another test revealed that tomatoes wrapped in the bacterial cellulose packaging material remained fresh for up to 30 days when stored at room temperature. Even after 30 days, the tomatoes demonstrated neither wrinkles nor microbial spoilage. Researcher Shivakalyani Adepu indicated that this is because, in addition to the antimicrobial activity, the composite also facilitates a favourable exchange of gases and moisture. “The material ensures that the fruit ages more slowly.”

Other applications

The research team aims to test the food packaging material on exotic fruit to see if the material will also keep this fruit for a longer period of time. Dr Khandelwal says that she would also like to test the same principle on medical products. “The composite can be used as an antimicrobial lining in sanitary napkins and disposable clothing and covering in hospitals.”

Source: The Hindu.

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We know much more about photosynthesis than about the flowering of the plant. This sometimes leads to surprises, especially with new crops. The grower has to take into account the juvenile phase, effect of temperature, light, size of the plant, day length, and the interaction between hormones, sugars and other compounds in the plant.

Before a plant can flower it first has to become an adult. Many plants have a juvenile phase. Even under optimal conditions they are unable to flower during this stage.
This is logical because a plant flowers in order to reproduce. Therefore the flowers must be of sufficient quality to actually achieve this. They have to be developed to the extent that they can be pollinated, for example by insects. And after pollination all kinds of processes need to start for the fertilisation and development of seeds and fruits. All of this costs a lot of energy. So from the plant’s point of view it’s considered ‘wise’ to postpone these processes until sufficient assimilates are available in the plant.

From juvenile to adult phase

The duration of the juvenile period varies enormously, from a few days to a few decades in trees. Of course, for the grower this can be very unprofitable if you have to wait a very long time for it to become productive. That’s why it’s good that a cutting or graft taken from a plant that is already in the adult phase also remains an adult.
The switch from juvenile to adult phase happens quite abruptly. The moment at which this occurs can depend on the size of the plant, age, number of leaves and growth factors.

Hormonal factor

From a wide range of research it’s clear that a hormonal factor plays a part in the transition from vegetative to generative. Suddenly the apical bud changes in shape as a forerunner to flowering. For a long time researchers looked for a hormone that stimulated flowering. The unknown flowering hormone was even given a name, namely florigen. But, it is now clear that florigen does not exist.
Although gibberellins play a role in many plants – this group of hormones was for a long time the leading candidate for the role of florigen – the situation is still ambiguous. In some plants gibberellins actually slow down flowering. Bearing this in mind, it’s also remarkable that growth inhibitors, such as daminozide, that slow the activity of gibberellin, do prevent the long and thin development of flowering plants, but not the flowering itself.
Another hormone group, the cytokinins, plays an important role in the induction of flowering. But again no general rules apply.
It seems that an interaction between hormones, such as gibberellins, cytokinins and ethylene, as well as sugars and other substances, such as polyamines, causes the induction of flowering. It’s different for every crop. The limited knowledge about the mechanism of flowering makes it difficult to effectively influence flowering. This is especially the case for new ornamental crops. Usually, the practical research focuses on achieving the most appropriate cultivation measures, without knowing exactly what happens inside the plant.

Leaves under first truss

Fortunately, a lot of research has already been done on the major horticultural crops. One of the many crops examined is tomato. A grower would like the plant to start producing quickly, and in terms of the tomato this means: the number of leaves under the first truss has to be limited.
In theory, a certain amount of assimilates must first be present in the tomato plant before it can start to flower. Indeed, research shows that any procedure taken to increase the amount of assimilates speeds up flowering. More light means fewer leaves under the first truss. A higher temperature at a low light intensity also leads to more leaves under the truss because the plant consumes more energy at a higher temperature.
As well as having a minimum quantity of assimilates, distribution is also important. At a lower temperature the top of the plant – the apex – has an advantage as it competes with the leaves.
This knowledge is difficult to translate into other crops. In fact the influence on flowering should be examined separately for each crop.

Short day = long night

A special phenomenon is the sensitivity of a flower to day length. In this respect, the origin of the plant makes a big difference. At the equator the length of day and night are the same and tropical plants are not day length sensitive. Plants from higher altitudes, that flower in the spring or even in the autumn, do tend to be sensitive to day length.
Sensitivity to day length exists as a result of natural selection. Therefore it’s also possible to remove this sensitivity by selection. By consistently selecting and further propagating the most insensitive plants it’s possible to solve this inconvenience. This doesn’t work sufficiently well with all crops, so we do encounter short day plants such as poinsettia, chrysanthemum and kalanchoe and long day plants such as gypsophilia, trachelium and carnation.
The naming is actually wrong. A short day plant is actually a long night plant because it’s all about the length of the dark period. And if this is broken – even for just a very short period – the whole effect of the dark period is lost.

Length of dark period

The plant registers the length of the dark period in its leaf but flowering takes place elsewhere. Therefore there has to be some communication between the leaf and the point where flowering occurs. This is carried out by a hormone that is produced in the leaf and then travels to the point of flowering.
How does the plant measure the length of the dark period? Previously researchers thought that the pigment phytochrome slowly broke down during the night into another form and that this was a signal to the plant to start flowering. But it’s more complicated than that. There is an interaction between the endogenous rhythms in the plant (‘the biological clock’). As a result the same length of darkness can sometimes produce different effects, whereby temperature can also play a role.
Some short day plants need just one long night. One of the most well known short day plants in horticulture is the chrysanthemum and it actually needs several weeks of long nights. If a grower stops the dark period prematurely, abnormalities occur. Just after a few short days the growth point becomes generative and stops producing leaves. Yet a grower has to continue with the long night regime for several weeks. It’s likely that multiple genes are involved in the flowering of chrysanthemum and it’s not simply a transition from vegetative to generative based on one gene that can be turned ‘on’ or ‘off’.

Mutual competition

Once the plant has switched from vegetative to generative and then flower buds have actually formed, many things can still go wrong. The buds can dry out or fall off and the flower may not open properly. This is mostly a question of how well the flower bud and the flower have been supplied with water, minerals and assimilates.
The flower has to compete with other parts of the plant and sometimes loses the fight. Optimal climate conditions, providing enough light and water, reducing the competition with the young leaves (by picking leaves) are all ways to ensure that flowering is successfully achieved.


A plant can only flower when it is mature. In horticulture, we bypass the juvenile phase by using cuttings and grafting. The transition from vegetative to generative appears to be controlled by a hormones. Flowering is the result of an interaction between several substances, for example, gibberellins. We still know too little about flowering which is sometimes difficult when working with new crops. A lot of research has been carried out on the major horticultural crops such as tomato and chrysanthemum. The latter is the best-known short day plant, although we should call it a long night plant.

Text: Ep Heuvelink (Wageningen University) and Tijs Kierkels. Images: Theo Blom (University of Guelph, Ontario, Canada).

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A tomato that has optimised its defence mechanism against insects will not only suffer less damage from caterpillars, but will also incite caterpillars to eat one another. This is a defence tactic that, until it was brought to light by a recent study conducted at the University & Wisconsin, has been hitherto unknown.

When tomato plants are attacked by insects, they produce antibodies in order to protect themselves. They actually start doing this as soon as other plants in their direct vicinity are attacked. This mechanism is activated when they detect volatile substances emitted by plants that are being eaten by predators. Researchers from the University of Wisconsin, led by John Orrock, sprayed tomatoes with volatile substances like these with a view to activating what is referred to as the jasmonic acid route. This defence route is activated to keep insects at bay.

Remarkable results

The American scientists wanted to investigate the details of this defence mechanism. They wanted to discover if the plants only ward off the insects (because they are unappetizing or toxic) or produce another detrimental effect on them (e.g. by inhibiting reproduction). The study was conducted with caterpillars of the small mottled willow moth (Spodoptera exigua). The results were remarkable: not only did the plants sprayed with these substances produce five times as much biomass, because they had barely been eaten by insects at all, but the caterpillars began to feed on one another As a result, their population shrunk notably.

Finding the right balance

It is known that caterpillars have a tendency towards cannibalism when faced with food scarcity. The researchers believe that the low nutrient value of plants in full combat mode triggered the increased instances of cannibalism. The effect of the altered composition of the plants has, until now, never been investigated. These findings have been published in Nature Ecology & Evolution. In an accompanying interview, John Orrock points out that the cost to the plant of activating its defences is very high: the plant has to invest heavily at the expense of its growth. He believes that plants will always strike a balance between maximum defence and accepting minor damage from predators.

Text: Tijs Kierkels.

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The Flavourfresh Solfresh group has the unwavering mission to be the most innovative and flavoursome tomato grower in the UK and beyond. The company has been supplying to leading nationwide grocery retailers including Marks & Spencer and Asda for more than 25 years, as well as to manufacturers of prepared salads, ready-meals, pizzas and sandwiches.

Based in Southport in Lancashire, the company currently has nine different varieties of tomatoes in commercial production, spread across 14 individual greenhouses on 125,000 square metres, generating around 2.8 million kilos of tomatoes a year. In addition the company produces 60,000 square metres of strawberries in seven individual greenhouses. The workforce in all the greenhouses plus the packhouses totals around 350 employees.
In charge of growing the tomato crop including R&D and trial material is Production Manager Andy Roe, who was named ‘Best Production Manager 2017’ at this year’s Grower of the Year awards in London. He has been at this nursery since the very start and truly embodies the company’s motto: ‘Getting flavour into fresh produce’.
“I’m continually scouring the world to find the ‘holy grail’,” states Roe. “The flavour is king. My personal number-one priority is to produce the best flavours, but of course with an economic ‘business head’ on. I will travel, explore and trial anything to find the absolute, very best flavour for the more discerning customer on the British high street.”

Striking the balance

Hence, Flavourfresh works with almost all seed producers and many different varieties, including Piccolo (cherry vine), Delisher (baby plum on vine), Amoroso, Edioso and Nebula – which is one of Roe’s personal favourites. “We have exclusivity on Nebula in the UK and supply it to Marks & Spencer and Asda, although I think I’m one of the only fools crazy enough to try to grow it. It’s very strong. To get the flavour that I want, I have to dominate and restrict the growth of the plant until it obeys me; I almost beat it into submission. It’s like ‘Fifty Shades of Lycopene’. In fact, my nickname is the Christian Grey of tomato growing”, he laughs. “But when you win the battle, it produces superb flavour and quality – although there is a yield penalty to pay for that. It’s about striking the balance.”

Developments in LED light

Traditionally, the seeds for the tomato season are sown from mid-October onwards. The majority of the plants are raised in Yorkshire, before being delivered for planting at the start of December. They are then harvested from mid-February through until the third week of November. However, this approach left with a gap in production from December to late February and the company was keen to extend its activities to an all-year-round season.
Roe explains: “High pressure sodium lights has been the standard technique for growing through winter for the past decade or so. However, our greenhouse doesn’t have sufficient height for the plants to be able to cope with the hot, aggressive light produced by these lights. Several years ago, we heard about the early developments in LED light. We tried several different light units from various suppliers from around the world, and that evolved into a commercial trial 18 months later. We discovered that this light is cooler, softer and more generative, plus the energy consumption and running costs are much lower. The trials proved conclusively that we had to do it.”

Quite astonishing

“The Philips Lighting solution stood out as being the most advanced, plus there were extra benefits in terms of technical input, back-up, support and professionalism,” recalls Roe. He ran comparisons with other solutions but the yield was so much higher that he calls the ultimate decision a ‘no-brainer’. “It also generated flavour, which I was initially sceptical about,” he adds. “The spectrum of mainly red plus a few percent of blue light that Philips has designed is spot on for tomato production,” he comments. “The results are quite astonishing, especially bearing in mind that the winters can be pretty dark in the northwest of England.”
Therefore, in August 2016, a 100% LED solution with two lines of horticultural inter-lighting and top lighting was installed on a full 4,500-square-metre block of the greenhouse at the Lansdale site.

New greenhouse

“The effect on the plants was mind-blowing, astonishing; words almost can’t describe it,” exclaims Roe. “The flavour, quality, size, plant balance, generative growth, everything was absolutely optimum for tomato growth during those winter months. We now take delivery of 50-day old plants for LED production in mid-September. We can start harvesting in early December and it takes us right through until the last few days of August. Then we stop harvesting, remove the crop and replant it within seven days,” says the production manager. So the company is now able to produce tomatoes all year round, currently of the Delisher variety, which has increased yield of its tomato crop by around 30%.
The results have been so impressive that Flavourfresh is keen to expand its use of LEDs, and is also trialling Nebula and other varieties to understand what else will perform well as a lit crop for the winter. But first, the company needs to complete installation of an additional 8 MW of CHP engines. “The current LED solution is at the Lansdale site, where a CHP engine was installed 14 months ago, so that dovetailed in nicely,” explains Roe. “We reclaim the CO2 from the flue gas and reuse the heat produced in electricity generation. A 3 MW CHP will be installed at our Melrose site by November this year. Once that’s in, we can build a new 16,300-square-metre greenhouse there – planning permission is already in place – taking our LED activities to 20,000 square metres from September 2018 onwards.”

Grow whatever you want

Over the past few years, many UK grocery retailers have significantly expanded the top-tier range in their tomato category to capitalise on consumer willingness to pay more for a superior taste. Underlining this trend, Roe says: “My wife is prepared to pay almost any price for her favourite chocolate, and the same applies to tomatoes in my mind. And that’s what LED lighting brings to the tomato market, a much better and more distinctive flavour. Many tomatoes in the premium range are being grown under lights throughout winter, and that’s accelerating now as other retailers join in.” In view of these market forces, the company believes that LED-based all-year-round production will become standard in the next five years, and growers who fail to keep pace with this development will simply be left behind.
In fact, Roe calls LEDs the ‘greatest horticultural innovation since the invention of the tractor’. “Just look how far we’ve come in the relatively short time that I’ve been growing tomatoes. Combined with today’s computer technology and automation, LEDs enable you to grow whatever you want in a dark room all year round, with perfect consistency and quality, and pesticide-free – and you can even control everything remotely on your iPad at home. The next evolution beyond LED will be incredible – and I’m looking forward to it.”


The UK-based Flavourfresh Solfresh group has an outstanding reputation for innovation and flavour, and has been supplying world-class fresh produce to British grocery retailers for more than 25 years. In a move to extend its tomato season throughout the winter months and achieve all-year-round production, the company has recently installed a 100% horticultural LED solution. The results have surpassed all expectations.

Text: Lynn Radford. Images: Flavourfresh.

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Several growing areas in the Netherlands and Belgium had to contend with them last year: Bemisia tabaci and tomato russet mite. These two pests are no strangers to the tomato sector but the intensity with which they appeared was unexpected and the damage they caused was considerable. Reason enough, therefore, to take a closer look at these insects. Advisors from crop protection suppliers Certis and the Delphy Knowledge Institute give their tips for preventing an outbreak.

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“Passion for perfection” – that’s Dutch tomato growers Schenkeveld’s slogan, and not without good reason. Production and quality are already at a very high level. But they can and should be even better, believes crop manager Berry Baruch, who is responsible for the crops at all three of the company’s sites. More focus on the root zone and constant monitoring of conditions in the slab throughout the day and the season make for optimum accessibility and uptake of water and nutrients. This strategy has delivered him a 5% increase in production.

Family-run Schenkeveld Tomaten has been growing tomatoes for almost 80 years. Richard Schenkeveld is the current owner of the company, which has three sites growing cluster tomatoes totalling 30 ha within a radius of three kilometres of each other. The tomatoes at the Schipluiden site and on two-thirds of the Den Hoorn site are lit, enabling Schenkeveld to supply tomatoes all year round. The nursery is a member of the Prominent growers association and sales take place via the Door Partners cooperative, which means that the quality bar is set high.

Irrigation strategy

Baruch takes every opportunity to not only steer the plant above ground via the climate but also below ground via the root environment. As well as relying on the automatic pilot in the climate computer, he likes to keep his own finger on the pulse to ensure that the water content and EC in the slab are kept as constant as possible. “Recently we had a spell of cold weather with a north-easterly wind. When that happens, you have to restrict your ventilation. In those conditions the plant takes up less water despite the amount of light available. You can’t automatically adjust your irrigation to that,” he says.
Baruch has two tools which he uses to manage his irrigation: an Aquabalance weighing scale and, since the current growing season at the Schipluiden site, the wireless GroSens sensor system from substrate suppliers Grodan.

Wireless sensors

The advantage of the sensor system is that it consists of several wireless sensors which accurately measure the water content, EC and temperature in the slab. A basic set consists of a receiver and three sensors which can be positioned anywhere in the greenhouse. The crop manager: “There are always differences in the greenhouse. I aim for the representative average of the measurements from the three sensors in the control section. Because it is a wireless system, you can easily move them to another slab if a sensor looks like it is deviating from the average, for instance if one of a plant’s four stems is lost. On top of that, we recently added a fourth sensor in the irrigation section at the back of the greenhouse. We use that to check that the measurements in the irrigation section at the back match those in the control section.”

Sensors and weighing scale

The question is why the crop manager needs both tools – wireless sensors as well as a weighing scale – to monitor his growing conditions. “To get the most out of the crop, I measure as much as possible. We start irrigating based on the amount of radiation after sunrise at the time when the crop actively starts to transpire. The EC peaks in the morning and drops away rapidly in the substrate after the first point of drain is reached. By taking more measurements with the wireless sensors I have a better picture of what is happening with the concentration of the nutrient solution and I’m not worried now if it rises by, say, 0.3 mS/cm2 in warm weather.”

Production up by 5%

Gert-Jan Goes, substrate and irrigation advisor at Grodan, adds that with this system, growers will notice if something is wrong one or two days earlier than if they only tracked the amount of drain water and EC. “If a plant isn’t happy, the concentration in the slab increases. As soon as you see that, you can adapt your strategy. By optimising your strategy you can push the boundaries a little further and increase the drip value on more days of the year.”
Baruch drip irrigates with an EC of 3.5 at the beginning of the crop and 3.1 later on. He sees clear advantages in this higher value. “The better the plant grows, the more nutrition it needs. We aim for a highly generative plant with high production, better quality and more flavour.” Goes adds: “By staying on top of things better you avoid EC peaks in the slab. You have to flush out any excess and that uses up more water. And there is less oxygen in the slab. The roots don’t develop as well and that costs you in terms of production and plant health.”
In the last growing season, Baruch’s use of the wireless measuring system enabled him to increase production by 5%. “The plants were potted up on 8 October 2015. We wanted to get the most out of them right up to week 20 2016. We got the extra production in the period in which both the costs (of lighting) and the yields were highest.”

One plant per slab

This increased production is not only the result of extra measurements but is also due to the fact that Baruch is using the Elite system at his Schipluiden site: one plant per 50x10x15 cm slab. “That means plants are not competing with each other in the root zone and makes the plants and stems more uniform. We aim for maximum uniformity in the root zone as well as an even number of stems per unit and an equal distance between the dripper and the drain hole for every plant.”
Goes adds: “Because the wool in these slabs is more capillary at the top, it retains water better there. The water is taken up more easily at the bottom so it is drier there. The balance between water and oxygen in the slab is better and this results in higher, more efficient uptake of water and nutrients. At the end of the day, you can continue to drip irrigate for longer without affecting root quality and generativity. This makes for more vigorous plants and heavier fruit.”

Set daily routine

The crop manager follows a set daily routine: re-saturate, flush, balance, reduce in the afternoon. Optimising the EC in the slab is an important task. He starts his day by re-saturating the slab. Once the point of drain is reached, the flushing stage starts.
The question is how far the EC drops in this phase. If he hasn’t got this under control before noon, something is wrong: the point of drain may have been reached too late, for example, or there may have been insufficient drain in this particular period. He tracks this by means of the wireless sensors. In the afternoon there is a balance between irrigation, uptake and drain, with a stable EC in the slab. He continues irrigating for longer at the end of the day. He also sees this reflected in his measurements. The water content drops more rapidly after the last irrigation; the plant takes up water over a longer period and is active for longer.

Water and fertilisers

An important requirement for all of this is good irrigation water. Schenkeveld Tomaten uses a combination of rainwater and reverse osmosis water, stored in silos and basins covered with floating tarpaulins. The combination of good irrigation water and skilful irrigating produces less drain: 30-35% in the lit period, 35% on sunny days and 25% on dark days. That’s 3-4% less than in the previous year, meaning less drain water to disinfect and less accumulation of minerals or rising sodium figures.
Baruch has to irrigate less to maintain a stable EC in this greenhouse than in the other one. As far as the total amount of irrigation is concerned, there is not much difference. “I continue watering for longer here. The sessions in the afternoon produce less drain but they translate into higher production and better growth. The stable irrigation gives the plants good, healthy roots which contributes to healthy plants and fewer problems with diseases.”
The plants at all three sites are nice and robust. In terms of production, the nurseries are up there at the top. By optimising their irrigation strategy using the wireless sensors and the one-plant-per-slab concept on special slabs, they have been able to go even further.


At one of its three sites, Schenkeveld Tomaten not only has a weighing gutter but also wireless sensors that measure the EC, water content and temperature in the slab. Crop manager Berry Baruch uses these extra tools to keep the root environment even more stable. This translates into a 5% increase in yield in the lit crop at a time when prices are good.

Text and images: Marleen Arkesteijn.