Sign up for our daily Newsletter and stay up to date with all the latest news!

Subscribe I am already a subscriber

You are using software which is blocking our advertisements (adblocker).

As we provide the news for free, we are relying on revenues from our banners. So please disable your adblocker and reload the page to continue using this site.

Click here for a guide on disabling your adblocker.

Sign up for our daily Newsletter and stay up to date with all the latest news!

Subscribe I am already a subscriber
6th International Grodan seminar:

A look at the future developments in plant propagation

More plant propagators than ever before, from twenty different countries, attended Grodan’s sixth international seminar, which was held this year in the historical Dutch ‘white town’ of Thorn. This time the focus was on future developments in propagation, such as the use of LED lighting in healing grafted seedlings. Another topic was a new method for purifying water that preserves the valuable nutrients resulting in healthy, resilient plants. A visit to Grodan’s stone wool factory in the town of Roermond and the Gipmans plant and herb nursery in Venlo offered the seminar’s attendees plenty to see and discuss.

The Greek plant nursery AGRIS uses LEDs to heal grafted seedlings in its high-tech growing chambers. AGRIS is an important player in the vegetable industry of Southern Europe. The nursery currently produces 12 million grafted seedlings a year of its main crops melon, tomato and cucumber. That’s 700,000 seedlings a week, and that figure is growing annually.

Damianos Kintzonidis, production director at AGRIS, explained to his colleagues at the seminar how his nursery has progressed from propagating grafted seedlings in small mobile greenhouse tunnels in 2005 to today’s high-tech healing chambers.

Better control in climate chambers
He explained how his nursery is acquiring more control over the climate parameters temperature, relative humidity, light intensity and the photoperiod, and that its transition from mobile tunnels to healing chambers built from insulating panels has meant a reduction in labour.

“Our mobile tunnels implied moderate climate control, intensive labour, high energy consumption and moderate control of the healing process, whereas our present healing chambers enable us to realise effective climate control with an autonomous heating and cooling system, good humidification and dehumidification, and efficient ventilation. We are also able to make more efficient use of the available space – from 3.2 trays/m2 in our mobile tunnels to 12 trays/m2 in the present situation with LEDs.”

From 2013 until 2015 the high-tech healing chambers were still fitted with fluorescent lamps. In 2015 AGRIS switched to using LED lamps. They move to and fro above the cultivation beds, so you need only one 32 Watt LED lamp per five trays.

Better healing and root development with LEDs
The fluorescent lamps caused problems because of their emission of heat, and the light spectrum was not optimal for the healing process. According to Kintzonidis, the switch to LEDs led to improvements in every respect: an optimum spectrum, no heat emission and low energy consumption.

Of at least equal importance is that the plants thrive under the LED lamps with the right spectrum, healing better and faster. It takes tomato seedlings only six days to heal, and cucumber seedlings seven days. The plants also have more active roots that develop better. And under blue light the plants remain more compact.

AGRIS is continuing its research in cooperation with partners such as the university of Thessaloniki. Aspects that are now being studied are the effects of new LED lamps with different spectra on the healing process, and the question whether LEDs may also be beneficial in the propagation of grafted plants and rootstocks, and during the hardening of the plants.

New water-purification method
Water IQ International specialises in the use and recycling of water in horticulture and the industrial production and processing of food. Jeroen Krosse, the company’s Director of Business Development, explained how they used knowledge acquired in beer-brewing to develop a new way of purifying water for use in greenhouse horticulture.

This topic is now of great interest among Dutch greenhouse growers because the requirements of the European Water Framework Directive will mean that, as of 1 January 2018, they will no longer be allowed to discharge unpurified waste water. “Our challenge was to improve both the consumption of water and the product’s quality. How do you get the best possible irrigation water? What do you want to remove from your drainage water before recycling it, and what do you want to leave in it?” – that’s how Krosse described the questions they faced. Contaminants, pests and pathogens, residues of crop protection products, and in some cases also sodium have to be eliminated. But substances secreted by plant roots to stimulate a varied microlife around the roots must be retained.

Good microflora
The new method is based on knowledge borrowed from the beer industry, in which Fusarium may cause problems during the malting process. By promoting the development of 'good' microorganisms you can shift the natural balance to reduce opportunities for Fusarium to develop.

Translated to horticulture this means that you can promote the development of 'good' microorganisms in the root zone by feeding them root exudates obtained in the purification and disinfection process. This varied microflora 'helps' plants to take up nutrients and repels pathogens from the root environment, resulting in a resilient system.

The Opticlear Diamond combines the aforementioned steps. It is a purification system that disinfects drainage water, ensures oxygen-rich water, eliminates residues of crop protection products and growth regulators, and selects the 'good' substances that boost the favourable microflora in the root environment. Krosse went on to explain how his company realised this. The resultant system has been approved for the discharge of purified drainage water after 1 January 2018, when the new regulations come into effect.

Latest developments
Hans van Herk, one of Grodan’s propagation specialists, discussed some new developments that started five to seven years ago, such as the plant type with three or four stems and the new way of removing leaves. “Topping seedlings to the cotyledons and then topping them once again, or topping twice to the second leaf results in plants with four stems. Such plants imply major advantages for growers – they get two or three extra trusses on the third shoot and they need fewer plants, and hence fewer seeds, per hectare. This is quite a challenge for propagators, as it’s not that easy to realise with some plant types, especially large tomatoes.”

Another new development is to remove leaves to create a good leaf balance along individual shoots, especially in summer and early autumn crops. In winter this results in delays of two to three days. Van Herk advised the propagators to experiment with these two new procedures at their nurseries. “Growers will start asking for them.”

Yet another trend is the demand for smaller plant holes in propagation blocks. “The advantages of this are a closer fit between the plug (20 mm) and the hole (22 mm), the possibility of more accurately checking the quality of your work and a more uniform initial development of the plants. The possibility of 22 mm plugs is even being considered.”

Stone wool production
On the second day of the seminar the propagators visited the Rockwool factory in Roermond and the Gipmans nursery in Venlo. Roermond is the home town of one of the three factories of the Rockwool Group that produces Grodan’s basic material. Jasper Bouwman, Business Director for North & West Europe at Grodan (Rockwool Group), provided a brief explanation of the composition of the mother company, and Grodan’s place in it. During the tour the propagators got to see how the stone wool is produced from the natural raw material basalt, and how it is processed into plugs, blocks and slabs.

Kwekerij Gipmans is a family business that is currently managed by the third generation. “We have a total greenhouse area of more than 68 football pitches, in which 125 employees produce 500 million plants a year,” said Thijs Gipmans. Besides young plants for the greenhouse cultivation of vegetables and for the cultivation of lettuce, cabbage and soft fruit, the nursery also grows herbs for the consumer market. Gipmans pointed out that the nursery aims to present itself as a sustainable producer, a good employer and pioneering in the adoption and development of new techniques.

The tour also included a visit to two of the six production sites. September is a relatively quiet month for the nursery and many areas were temporarily empty, just before the start of the busy season of the propagation of the young greenhouse vegetable plants. The visiting propagators were particularly interested in specific cultivation techniques, such as the mobile heating elevation, the extent to which Gipmans follows the new energy-saving cultivation principles, and the labour-saving machine for installing plant supports.

For more information:
Publication date: