“Knowledge of soil organisms is key in ideal potting mixture”

“Knowledge of soil organisms is key in ideal potting mixture”

Bark, the main ingredient of orchid substrates, is steamed at high temperatures. This kills off all the impurities and pathogens. But unfortunately it also spells the end of a lot of good things. What remains is a sterile medium – and try growing a resilient crop in that. After all, a healthy plant starts with a healthy root package. So VG Orchids does the logical thing: it has soil organisms added to its substrate.

Adding additives to substrate restores the natural symbioses and creates a healthy environment for the roots. This brings Phalaenopsis growers one step closer to the ideal potting compost.

Over the years, family business VG Orchids, which has two branches in the Dutch town of De Lier and includes the innovative brand VG Colours, has grown from 2,000 m2 of cut Phalaenopsis to 12 hectares of pot orchids. The plants are supplied in 6 and 12 cm pots. Cultivation manager Otwin van Geest has been working exclusively with the new Infigo substrate from BVB Substrates at their main branch for a year now. In addition to bark and pH buffering peat, this mixture contains several additives to ensure stable soil life and good resilience. An important part of this is the microorganism Trichoderma harzianum T-22 (Trianum) from Koppert’s NatuGro package.

Reducing chemicals

A good substrate forms the basis for healthy roots and a resilient plant. But the way in which this knowledge is used varies from grower to grower. For VG Orchids, the choices they make in this area are key to successful and sustainable Phalaenopsis cultivation.

The company therefore follows developments closely, working with their substrate supplier as a regular partner. They too are constantly pushing the boundaries: innovation is a vision both companies share. Van Geest: “We want to progress, and as long as we can see improvements happening, we’re happy to sit down with the customer and come up with solutions. Our ultimate goal is not the mixture per se but rather to reduce our use of chemicals. Crop protection products often stunt plant growth. Besides, as a grower you want to cut down on the amount of chemicals you use. So we are looking for other ways to keep the crop healthy. A resilient plant can solve a lot of problems itself, so we’re fully behind this development.”

Natural resilience

The cultivation manager likes to make the comparison with people. “If a person is regularly exposed to good and bad bacteria in their immediate living environment, they develop a healthy immune system. Then, if they are exposed to increased levels of a pathogen, they will be less likely to fall ill than someone growing up in a sterile environment. And so it is with plants too.”

That is why the environment around the roots is so important, he believes. “There must be enough oxygen and soil organisms in the pot to ensure optimum uptake of important elements and nutrients. And when you can no longer be certain that that is the case – if the substrate is sterile – you have to add those components artificially. In our current mixture, for example, the peat helps the organic elements bind together well and Trianum protects the roots against harmful fungi.”

Thoroughly trialled

The search for the ideal potting compost is a continuous process in which new information and knowledge is constantly being incorporated into solutions. VG Orchids facilitates a think tank that meets regularly to exchange experiences. It is attended by the cultivation manager, a specialist from Aqua Terra Nova, a microbiologist and cultivation specialist from BVB Substrates, a specialist from Koppert and adviser Peter Klapwijk.

“Following these meetings, which we hold once every ten weeks, we usually set up five substrate trials here,” says Van Geest. “Important aspects we test are the proportions of bark, coir, sphagnum and peat, with and without various additives. Previous cultivation trials have shown that the Infigo mixture is best for our company in terms of crop steering. As a result of the research conducted by the think tank, further improvements have been made to this mixture in the form of plant strengthening additives. The results are positive. The pots are full of healthy roots and leaf surface has increased by 20 to 25 percent.”

Continuous measurement and refinement

This collaboration is also worth its weight in gold to the substrate supplier. Orchid specialist Robin Camphens: “We are an innovative company and we want to stay ahead. With this in mind, we recently hired a microbiologist. His expertise is very enlightening and gives a real boost to our work developing new potting compost mixtures. You only need to look at VG Orchids, where he advised on the successful additives for the substrate. Soon, when our new research centre with phytotrons comes into operation, we will be able to focus even more specifically on orchid solutions.”

Camphens’s colleague Richard Bremmer regularly visits the orchid company to monitor the trials. He also checks the performance of the “standard” substrate, of course, and takes soil samples for a complete chemical analysis once every six weeks. The peat in the mixture makes this research possible. Koppert also carries out plant sap, Trianum and soil nutrient web analyses. Once a week, the grower monitors growth in plant height and width and measures the pH and EC. The results are discussed, following which any necessary adjustments are made to the growing formula or new trials are set up. In short, it’s a continuous process of measurement and refinement.

Successful teamwork

The two partners hope to be able to observe more effects of the new substrate in the near future. Bremmer: “We expect a more resilient crop to lead to fewer losses. And of course the quality should be better too: a healthy plant branches better and produces lots of buds. I am gradually seeing an upward trend. Of course, resilience depends on several factors. Your crop protection strategy must be right, you must get your hygiene right – that sort of thing. But the main focus is still on the root environment, and our grower-specific potting compost mixture is an important step in this direction.”

Van Geest appreciates the supplier’s input. “Their knowledge is pure added value for us. We have every faith in their people and their product. The quality is consistent year round, and orchids appreciate that; inconsistency leads to stress and stunted growth. And as a grower, that’s something you want to prevent at all costs. A resilient plant can do so much more.”


The Dutch pot plant company VG Orchids has switched to a tailor-made substrate for Phalaenopsis. Standard potting composts are often too sterile and VG Orchids hopes to create a healthier climate for the roots with additives like peat and Trianum. A good mixture is the basis for a strong root package and, ultimately, a more resilient crop. This resilience should reduce stress and offers growers an opportunity to reduce their use of chemicals.

Text: Jojanneke Rodenburg.
Images: Studio G.J. Vlekke.


Water treatment system maintains optimum oxygen supply

Water treatment system maintains optimum oxygen supply

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.


Cultivation fabric with good water permeability and temperature distribution

Cultivation fabric with good water permeability and temperature distribution

The improved water permeability was a specific request from users. The fabric is also UV resistant, making it suitable for use anywhere in the world. The light reflectivity matches the growing seasons, reflecting the right amount of light in the summer and absorbing the right amount in the darker months. It also retains heat when necessary and doesn’t absorb heat at times when the plant doesn’t need it.

The ErfGoed Grey Cover was developed based on extensive customer feedback, with the manufacturer also making use of new insights and technologies from various suppliers and research institutions. The product is a seamless enhancement of the total concept of the Excellent cultivation floor – in other words, providing the plant with the right amount of water at the right time.
Stand number: 11.500


Yields can be increased with new slab

Yields can be increased with new slab

Grodan develops crop-specific product solutions to meet growers’ requirements. Trials have shown that yields can be increased by up to 5% with this new slab.

Grodan Supreme slab, which was specifically developed for the V cultivation system, is slightly narrower and higher (12×10 cm) than other slabs used in the cultivation of sweet peppers (15×7.5 cm).

New NG2.0 technology

Thanks in part to new NG2.0 technology, this slab offers some major advantages: fast, uniform initial saturation, more efficient use of the entire substrate volume and even better distribution of water and nutrients, especially at the top of the slab. The water content (WC) and EC can be more quickly and more accurately corrected. And all this is entirely in accordance with Precision Growing: maximum year-round performance through the efficient use of water, nutrients and energy. The plants form more healthy, fine roots in the upper part of the slab, ensuring more vigorous growth.

Stand number: 08.316


First tentative steps with biochar turn out positive

First tentative steps with biochar turn out positive

Biochar is a type of charcoal which looks set to become widely available on the market in future. This product could have potential for horticulture: as a soil improver, a peat replacement or enriched with beneficial soil life. A small number of nurseries have been trying it out.
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Christian Westhoff of leading German bedding and patio plant nursery Westhoff takes a keen interest in plant invigorators. “There is a lot of pressure on the use of crop protection products and inhibitors, so we are looking for other options. We have had good experience with products from the Austrian company Multikraft but they have to be sprayed and we want to avoid spraying in the spring as far as possible. Spraying increases relative humidity and, with it, the risk of a Botrytis infection. We were looking for a product we could mix into the potting soil and we came across biochar from Carbon Gold. Our substrate supplier mixes it in for us,” he says.

Crop brought on earlier

Last season the nursery ran large-scale trials with different varieties of calibrachoa and verbena. Westhoff is happy with the results. “The plants were very vigorous and yet they stayed nice and compact. We had to use less inhibitor than usual, which helped bring the crop on earlier, as inhibitors always delay flowering. The cultivation period was 10 to 14 days shorter so we were able to save on labour and heating. Whether it also made the plants less susceptible to pests and diseases, I can’t say at present.”
He does find the product a little on the expensive side, however, given that he can’t command a higher price for nicely shaped plants. So next season he will be trying out potting soil with various concentrations which he hopes will indicate the minimum amount needed to obtain a positive effect.

Bio-based economy

Biochar looks a lot like charcoal. It is a by-product of biomass pyrolysis and gasification, which are methods of extracting gas and oils from organic matter. In the transition to a bio-based economy, processes such as these will become more and more widespread, likely resulting in large amounts of biochar becoming available. Also interesting is the fact that it stays stable for a very long time – up to 1000 years – thus sequestering carbon and preventing it from being released into the atmosphere as CO2 and adding to global warming.
Researchers worldwide are looking into whether the product can play a useful role in agriculture or horticulture. There are three areas with potential: as a soil improver, as a replacement for peat in potting soil and as a carrier of microorganisms. The research results are variable but there do seem to be opportunities in all three areas, although a lot will depend on the method by which the biochar is produced.

Own “fortress”

The UK company Carbon Gold has already seized the initiative. It produces biochar from four Fairtrade FSC wood species, which is then processed. “The porous product acts like a sponge on nutrients,” commercial manager Cor-Jan van der Elzen explains. “So we add seaweed for the trace elements, and worm casts, which are rich in minerals and beneficial soil bacteria that convert the casts into fulvic acids. We want to boost soil life, so we also add trichoderma and six species of mycorrhizae.”
Improving soil life is something growers are particularly interested in. One way to do that is to add beneficial organisms to the soil. That doesn’t always deliver the desired results, however; beneficial organisms sometimes find it tough to compete with existing organisms in the soil. By adding them to charcoal pieces, you can create a little “fortress” where they are in the majority and from which they can go out and conquer the soil. That’s the idea behind enriched biochar.
Most of the experience with the product is currently being gained by organic growers. Cultivation specialist Wim van Marrewijk of the Frank de Koning Nursery in Tinte in the south-west of the Netherlands is using it for the second year running. “In the first year we added the unenriched form into the top layer of soil along with compost. That gave us a slight improvement in the growing layer, but after 17 years of growing organically the soil structure was pretty good anyway. In the second year we used the enriched product because we were having problems with nematodes, which transmit fungal diseases,” he says.

Extra generativity

He set up the trial with three repeats in order to be able to draw definite conclusions on the effects. These will only be known once the season is over. But he already has some first impressions: “In our tomatoes we are seeing a much stronger crop and less disease pressure. I also get the feeling that the plants are less susceptible to true and false mildew. The crop is more resilient to a high plant load than the plants without enriched biochar. At present we are hardly seeing any difference in sweet peppers.”
Van Marrewijk has already asked his plant breeder to add enriched biochar into the seedling compost as he firmly believes that young plants should be given the best soil life right from day one. William van Schie, head of organic plant cultivation at Grow Group in Naaldwijk (Westland, the Netherlands) says that several organic customers have asked for this over the past three years and are coming back again for more. “In tomatoes it produces some extra generativity and a darker leaf colour. Cucumber growers are especially keen as they are interested in the protection against nematodes it offers.”

Initial impressions

There is as yet virtually no experience with biochar in the conventional vegetable sector. Van der Voort Tomaten in Vierpolders – also in the south-west of the Netherlands – is using it for the first time this year. “We are looking for ways to improve crop resilience, and I liked the sound of this,” says Joost van der Voort. He is running a trial at his 8,000 m2 nursery in which the enriched form has been scattered under the blocks. The grower can only give his initial impressions so far: “I am seeing a slightly finer root system and more branching. There is nothing to see above ground yet. But we have a good feeling about this and we believe in the concept of introducing microorganisms. And then we’ll start measuring properly.”
Chris Blok of Wageningen University & Research in the Netherlands is conducting a series of experiments into the options for biochar. The first experiment revealed that the use of biochar in horticulture depends very much on the properties of the various types of biochar. Depending on the source material and how it is processed, the product can easily become too salty, too alkaline, not sufficiently porous or contain toxic substances. From this perspective, not all large anticipated residual streams will be of immediate interest to the sector, he believes.

Scientific evidence

In the Enerchar project, Wageningen University & Research, ECN, Dahlman and Klassman-Deilman are looking at combining heat and electricity generation from biomass with the production of horticultural-grade biochar in order to maximise energy efficiency. In previous trials with pot plants, it measured up well with peat, coco and wood fibre as a potting soil component forming up to 50% of the volume.
In the current study the product is enriched with microorganisms. As yet, the microorganisms don’t stay alive for long enough in the charcoal product produced in this way, but Blok believes this problem can be solved. Next he wants to set up trials to specifically investigate the effect of this method as a “fortress” for beneficial organisms. “Some scientific evidence is still needed in this area, quite apart from other effects of biochar such as structural improvement or nutritional effects. That evidence has been provided satisfactorily in controlled lab conditions but not under field conditions. Even if the individual species don’t survive well, the function – the combined effect of the microorganisms – might.”


Biochar is a charcoal product that can be used as a soil improver, peat replacer and carrier of microorganisms. Researchers worldwide are looking into whether the product can play a useful role in agriculture or horticulture. Practical experience is still very limited: a few growers are reporting positive experiences, with most of the experience currently being gained by organic growers. The researchers’ results are varied.

Text and images: Tijs Kierkels.