Whoever enters a greenhouse and looks at the substrate in the gutters will increasingly see alternatives to rock wool, often still combined with a rock wool block on top, although there are now organic alternatives for this as well. Delphy's advisors also see the trend. They assist growers in transitioning from growing on rock wool to alternative substrates, for example in cucumber cultivation.
What are the concrete alternatives to rock wool in cucumber cultivation?
A non-organic option is perlite, says Rens Smith, advisor for greenhouse vegetables and the manager of Delphy's greenhouse vegetables team. Abroad, his team sometimes also sees a type of lava granules as a substrate.
"Where we are currently seeing a shift is towards a potting soil mix and more coconut. This can be both in containers and in mats. This depends on the grower and also on the cost of the substrate. Loose fill is simply cheaper, and filling the containers, if done every year, is still a winter job."
What are the advantages and disadvantages of this?
For perlite, Rens knows the pumps must be large enough. "This will work for most companies but not just anywhere. With perlite, you retain very little water in the substrate, so frequent watering is a must. It is also a slightly more dangerous substrate if something goes wrong with the water system on a summer day."
The advisors from Delphy sometimes encounter the perlite itself in the drainage pit for years. "This is dangerous from a virus perspective. It is a clean substrate, as it is expanded rock, which is highly heated during production. A disadvantage is that it takes quite a bit of energy to make. An advantage is that perlite is relatively cheap to purchase."
Organic substrates have the advantage of increasing plant resilience, the advisor sees. "The bio-life in the mat is easier to add and stays alive longer. In an inorganic substrate, you keep dripping (bio)agents and often hope for the best, and it does seem to work in practice."
A proper balance in the mat seems easier to achieve in organic substrates. "The roots also seem to be more comfortable in the substrate, but this may be because they first grow around the substrate before growing into the mat," Rens notes.
The disadvantage of growing on organic substrates is that not all agents can be dripped without first thinking carefully, he emphasizes. "Some agents are bound to the substrate. Waste of your agent! We can prevent this by thinking about the timing of application. In addition, with these types of substrates, you often have to give a bit more, depending on the fractions and setup of the substrate. The substrate may seem wet enough, but appearances can be deceiving."
In cultivation, Rens sees that with organic substrate, the crop tends to be a bit more vegetative. "This means more energy in growth instead of fruits. This can be managed and is sometimes desirable for certain types. A slightly more vegetative growth is not always wrong."
For more information:
Rens Smith
Delphy
06 26 51 86 49
[emailprotected]
www.delphy.nl
