Demonstrating a fossil-free cultivation concept for tomatoes: that is the goal of the cultivation that starts on August 11 at the Delphy Improvement Centre. The seventh batch is flowering, and the team is already looking forward to the first harvest, which is expected to take place in three weeks. In the first phase of the growth, the development of the crop has been judged as positive by BCO.

With the planting date on the ides of August, the goal of the first phase was to keep the development speed high, while keeping the crop from overgrowing. In this phase of the growth, the surplus of light was screened by deploying the Harmony screen. After two weeks it turned out that the crop was too full, and required generative screening. This was realized by increasing the EX, the maintaining of a low level of nitrate in the dripping water, and the realization of a higher peak temperature on a day. This worked well, but now the growers have to be aware that the crop does not get too generative. They monitor the ratio between leaf and fruit growth weekly, to control the crop as well as possible.

Using greenhouse equipment to the fullest in the coming period
With the light outside diminishing, and the assimilation demand increasing, the day is started with lighting. The SON-T lights are turned off at an irradiation of > 300 W/m2 and the LED interlighting at an irradiation of >500 W/m2. The compartment is equipped with an active dehumidification system to regain the latent heat. In the coming period the balance between heat harvest and heat use has to be established. On the one hand this means harvesting enough heat, and on the other hand the heat input has to be controlled. The cultivation strategy is the basis for deploying active dehumidification. The moist deficit is leading in the control. On colder nights two screens are deployed to reduce the heat demand in the compartment.

In the coming period the outside light dwindles further, and the temperature decreases. The greenhouse equipment that contributes to the integral approach for an optimal climate (three screens: Harmony diffuse climate screen, Luxous energy screen, and Obscura light emission screen, hybrid lighting, clear glass, active dehumidification and a new hybrid water dispensatory system) has to be deployed optimally in the coming months to achieve the maximum cultivation results.

This project is financed by Kas als Energiebron, the innovation and action program by the ministry LNV and LTO Glaskracht Nederland. Saint Gobain Cultilene, Van Dijk heating, Ludvig Svensson, Hortilux, Hoogendoorn and Wireless Value also contribute. The project is executed by Delphy, Groen Agro Control and WUR Glastuinbouw.