"If you don't have it, get it," say Ton Habraken from Svensson and René Beerkens from Hoogendoorn Growth Management. They're talking about net radiation meters for greenhouse growers as they kick off the afternoon program of the Masterclass Smart Growing with Data. And place the sensor directly above the crop." That's where measurements should be taken, not above the concrete path or the heating pipe, which would distort the readings.
The net radiation meter indicates that it's beneficial to partially close the screens at the end of the day in order to reduce radiation and help maintain a stable temperature, allowing the crop to rest. Says Ton: "Don't look at the greenhouse temperature, but at the water absorption. A large part of the plant resistance is also contained in this."
Ton Habraken, Svensson, and René Beerkens, Hoogendoorn Growth Management, as day moderators 
Adrie van Kester, Sven Barendsen (BK Plant), and Willem Kogeler (Van de Knaap Substrates) 
Stefan van Os (Svensson), Stijn Jochems (Plant Empowerment), and Vincent van den Burg (Dalsem) 
Marco de Groot from Flori Consult Group
Gerbera versus vegetable cultivation
Marco de Groot from Flori Consult Group asks everyone to raise their hands. The few raised hands reveal that gerbera cultivation focuses on the PAR (Photosynthetically Active Radiation) sum, unlike in vegetable cultivation.
The PAR sum provides gerbera growers with valuable control for planning their cultivation. This precision is crucial because retailers demand specific quality standards at specific times for extended periods. If growers miscalculate, even a 10% overproduction or underproduction can lead to significantly reduced earnings.
The PAR sum is a key factor in managing gerbera cultivation, affecting areas such as CO2 levels, daily temperature, water supply, and shading. These elements are vital because gerberas react strongly to changes in radiation, light exposure, and temperatures of both the greenhouse and the plants.
Gerberas are quantitative short-day plants, meaning they bloom faster and more uniformly with shorter days (11.5 hours) and slower on longer days. With this information, growers can manage production. By increasing the darkness period, especially in the fall, higher production can be achieved.
Since 2005, Son-T light has been introduced in gerbera cultivation. The result was better winter production, less Botrytis and a more even production. The light levels gradually increased over the years, which created a problem with excess heat and humidity. The need for energy saving came into play. LED was the solution. "With LED, we experience, among other things, a large influence of outside radiation on greenhouse and crop temperature and also more influence of net radiation on growth and quality. And LED has not caused more quality problems."
Joeri Everse (Agro Care) and Gert Jan Wesselink (Looye Kwekers) 
Leo van Uffelen (Koningsrust Cultivation Advice), Hans Belt (Royal Brinkman), Sil Lek, and Tim van der Hoorn (HDP Pot plants)
The Masterclass was organized by Tomatoworld, Hoogendoorn Growth Management, Svensson, Kas als Energiebron, and Glastuinbouw Nederland. Heleen Lugt from LetsGrow.com and Jan Enthoven from Tomatoworld provided attendees with tools to develop their own cultivation strategies using the Strategy Manager. This program from LetsGrow.com allows users to input desired parameters like head thickness, stem density, and fruit weight. It then calculates and presents various cultivation strategies, enabling growers to optimize their processes independently.
The crop measurements are also entered during cultivation. Heleen recommends having the same person do these measurements every week.
The cultivation analysis will then follow automatically. Jan Enthoven: "Keep paying close attention yourself. The model is based on weather forecasts. Unfortunately, these are not always accurate. So you will have to adjust from time to time.
Alfred de Vreeze (Fotoniq Par*), Peter Barendse, and Jan de Winter (Syngenta Flowers) 
Ton Habraken (Svensson), René Beerkens (Hoogendoorn Growth Management), Jan Enthoven (Tomatoworld), and Heleen Lugt (LetsGrow.com)
Everyone went home with valuable insights plus, for those directly related to cultivation, the latest addition from Plant Empowerment on digital cultivation.