Water Source & Field Locality:
The source of water, being borehole, is stored on site in a galvanised water storage tank. From storage, the water is being pumped around a nursery by means of an existing 8m³/hr pump. The propagation system draws from this pumped system into the glasshouse, housing the propagation application.
Coolnet Pro Cross 4 x 5.5l/hr applied 1m x 1m spacing suspended on 20mm Black LDPE laterals suspended above the Blue Berry crop, which are set in trays on table in each zone. The zones are each treated separately, and are separated by a unique tent structure over each zone within the glasshouse itself.
Each zone, requiring just under 5m³/hr is controlled by a 1 ½” 24VAC Netafim Aquanet Pressure Regulating Angle Valve. The trigger of each zone is a humidity sensor set centrally to the zone, linking back to a multicore controller. A humidity set point is defined by the grower in the controller, which once reached in the zone and sensed by the humidity sensor, triggers the valve to open. Valve triggers are prioritised, with no more than one valve running at a time. Should triggers be in quick succession, the controller “stacks” the programmes, and waits until the previous valve has completed its run. Valve opening times (durations of burst) can be pre-set in the controller, allowing very short bursts (or pulses) at a time. The aim is to achieve a very high humidity of 98% within the environment, with a light “dew” settling on the leaves of the cutting.
The main line comprises a simple 50mm PVC Pipe lay-out, from pump point to the propagation zones.
As water is sourced externally (as mentioned earlier), this feeds into a 10, 000L plastic storage tank acting as a buffer. From this tank, water is pumped at low pressure through a acid dosing rig into a second 10, 000L tank. The acid rig injects Phosphoric Acid as water passes through into the second tank. It also has the feature of testing the pH of the water stored in the second tank from two points set in the wall of the tank. pH is controlled to a level of around 5.5.
From the second tank, two 5m³/hr Hydrovar controlled pumps set in duty-assist boost the water into the system. They are set with a 50% redundancy, where one pump runs a cycle, and then the next pump would facilitate the next cycle, distributing wear across the pumps. The system, being a pressurised set-up, reacts to pressure drop once a valve has opened, allowing the flexibility of hand watering where required without having to get the controller to start the pump, or manually starting the pump for this purpose.
The system has been planned with extra pump capacity to allow expansion and addition of overhead watering requirements in other areas of the glasshouse, as well as a proposed strawberry propagation system at a later date.
This propagation application has allowed the grower to not only concentrate on conventional propagating requirements, but also introduces the element of pH control and humidity based triggers across the system, on which Blue Berry plants thrive.
The system has been designed to allow for a certain amount of water storage in house, as having to rely on an external source that may at times have a higher demand on its source. Further to this, the pumping capacities, and the flexibility the controller offers in stacking programmes, allows for better expansion prospects of said system across the house in the future, without detriment to the crucial propagation based systems.