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Rijk Zwaan chooses to use Plantop blocks

Rijk Zwaan chooses to use Plantop blocks

The uniform treatment of several small batches of plants requires the use of easily managed and uniform mineral wool blocks. Blocks that will also provide optimum conditions for plant development. Following tests carried out two years ago at the Production and Breeding departments at Rijk Zwaan in De Lier, the GRODAN Plantop Delta and Plantop Vitagreen blocks proved to be the best and are now the blocks of choice for the cultivation of young plants.

The crossing results that require further testing are kept on the crop floor of the Breeding department. “We sometimes plant as many as 1800 plants comprising a total of 1500 batches including different numbers of plants. These can include small batches of one to five plants”, explains Lajos de Roo - the member of staff responsible for plant propagation in the Breeding department. He grows two batches of sweet pepper and tomato plants during the course of a year and cucumber plants all year round. The testing of young plants is carried out during the off-season. “We cultivate these plants in order to identify a variety of growth issues at an early stage, such as curly leaf with tomatoes or split heads with sweet peppers. We also check batches of seed that are intended for commercial use. All products must satisfy our stringent requirements.”


De Roo chose to use Plantop blocks. “I was convinced by the excellent results achieved with sweet peppers and the other vegetable varieties. In the past, we had experienced problems cultivating pepper plants in non-capillary blocks”, he explained.
The uniformity of the blocks has provided him with a degree of certainty. “We often have a number of different sized plants growing together. Especially during the second half of the cultivation term. The uniform water absorption of the blocks avoids the problem of variation in the moisture content of the blocks.” Other advantages include the promotion of sturdy and healthy roots throughout the entire block.

However, De Roo admits to having followed a learning curve. “Knowing that the block resaturation is adequate and the moisture content remains uniform, I can allow the blocks a longer drying-out period than initially was the case. Before irrigating, we now observe a moisture content of 300 g per block or even less depending on the weather conditions. This helps in the identification of the female cucumber plants. “We are looking for flowering plants. If these blocks can be kept less moist, this will accelerate fruit yield and promote compact plants.”


Benjamin Luijendijk is the plant cultivation foreman in the Production department. He supervises the cultivation staff and arranges the technical aspects of cultivation including irrigation and climate control for the vegetable plants for seed propagation. The main harvest comprises tomatoes, sweet peppers and cucumbers. 
He had already experienced good results using the Grotop Master slabs. So he decided to continue with this method, opting for a combination with Plantop blocks due to their reliability and flexibility in management. “When the water has been absorbed by the plant, the block is simple to re-saturate.” 

He also finds uniform root growth throughout the block important. “You can see this when you open the block. The roots should be just how you want them. When you place the block on the slab, it takes root almost immediately. This promotes even better plant growth.” The 0.5cm top layer encourages less algae with hardly any risk of Sciara flies.

Luijendijk agrees with his colleague - he is happy with the high degree of uniformity within and between the blocks which allow him to keep the relative moisture content between the pots as low as possible irrespective of plant size. “Our situation differs to that of nurseries. They have hundreds of thousands of plants of one variety. We deal in many different varieties.” 

Another advantage provided by uniformity is the convenience. “Irrigation can easily be assigned to a different staff member during the weekend. In the past, irrigation was based on instinct. We now weigh the blocks to determine the need for watering.”