In many ways, the setup of a rockwool or substrate growing system for vine crops is simple and inexpensive. The irrigation/feed system itself is a simple drip irrigation system with a dripper capacity of 2 liters/hour and one dripper for each plant. The nutrients are supplied using a two-head injector and fertilizer concentrate tanks. By knowing the bicarbonate concentration of your raw water, the appropriate amount of acid can be added to your concentrate tanks so that the pH of your feed solution is between 5.5 and 6.0. Remember that it is important to have your raw water analyzed so that a properly balanced nutrient formula can be mixed.
Timing of irrigation can be accomplished by simply attaching a timer to a solenoid valve in the feed line. Irrigation controllers are also available. For rockwool growing it is possible to use an irrigation control tray. This tray indirectly measures the water content of the rockwool slab and triggers and irrigation when the level drops below a set amount. This system automatically provides water based on plant demand giving the grower more time to spend managing the crop.
The exact layout of the greenhouse depends upon the crop grown. Generally, the floor is covered with white or preferably black and white poly. Rockwool slabs are placed in the rows, holes for plants are cut in the plastic surrounding the slabs and the drippers placed in the holes. The irrigation system is turned on and the slabs fill with solution. Seedlings are placed on the slabs and drainage slits cut in the slabs as well as the plastic floor.
The key factor in managing the system is measuring the pH and EC in the slab. Samples should be taken in the morning, more often if possible. Even though the substrate has a considerable buffering capacity, the EC and pH may change during the day. The concentration of salts in slab are managed as previously discussed. Eventually, the grower acquires a feel for how much solution the crop uses in a day and how the pH and EC change. He can then adjust the frequency and time of irrigation in anticipation of these changes.
