Fertigation Controllers

Fertigation Controllers are the driving force behind modern commercial greenhouse fertigation systems.

Fertigation is when refined soluble fertilisers are mixed with water and fed to a crop.

Fertigation Controllers are predominantly used to operate drip fertigation systems where plants are grown in media filled slabs or bags and the nutrient solution is delivered to the root zone of the crop via pressure compensated drippers.

A standard irrigation controller can only activate an irrigation pump and solenoid valves but is unable to dose nutrient stock solutions. The nutrient dosing must be done by a separate dosing controller.

In comparison, a Fertigation controller is an all in one unit.

It doses nutrient stock solutions and pH corrector to predetermined set points and it is also able to operate solenoid valves to deliver this nutrient solution to multiple zones within a greenhouse in response to environmental triggers (e.g increased light intensity).

Advanced Fertigation controllers can manage each fertigation zone individually so that each zone can have its own EC and pH setpoint, its own individual recipe if required as well as customised fertigation times. This allows a single crop type of different ages, or a variety of different crop types to be grown under one roof and fed from the same hydroponic system.

The Fertigation controllers are connected to professional environmental sensors which are suspended from the greenhouse roof to monitor sunlight, relative humidity and temperature inside the greenhouse. For outdoor crops a professional weather station can be installed to monitor wind speed, wind direction, rainfall occurrence and rainfall volume. All of these collected readings are then cross referenced and used to trigger more or less fertigations as required.

The beauty of using an advanced fertigation controller with environmental sensors is that it ensures that the plants are only fertigated when necessary, with no overwatering.

Valuable nutrients and water resources are therefore conserved.

Solar irradiance is used as the main environmental trigger point. If solar irradiance is high then the plants will be transpiring at a higher rates so more frequent fertigations are required. If it is low then less fertigations are required.

A solar integrator is used to counts the level of solar irradiance as it enters the greenhouse. The higher the light intensity from the sun, the faster the solar integrator will count and each fertigation will be triggered in quicker succession.

There are two types of fertigation systems commonly used.

Batched Dosing Drip Fertigation Systems 

These systems are commonly used for small to medium greenhouse systems. A mixing tank (e.g 2,000 litres) is automatically filled with water, dosed with nutrient stock solutions and pH corrector to a predetermined strength, stirred and then fed out to the crop.

If each zone requires a different nutrient strength or environmental trigger, then the tank is automatically filled up by only a small amount, dosed, stirred and then fed out to Zone #1. The controller then goes on standby as it waits for the next trigger to signal which zone needs fertigating (e.g The solar count for Zone #3 reaches its maximum). The tank is then refilled with fresh water and then dosed to the strength required by Zone #3 and this is then fed out to that zone.

If only one nutrient strength is required for all Zones then the tank is filled to the top, dosed, stirred and then fed to each zone one after the other or in accordance with the environmental trigger set for each zone.

The controllers can also draw from one or more ‘B’ tank solutions to enable different nutrient nutrient recipes to be used for different crop types fed from the one system, or for adding any special additives which may be required throughout the day.

Inline Injection Drip Fertigation Systems

 These systems are designed for large greenhouses with a large number of irrigation zones containing  large numbers of plants, with each zone requiring individual EC and pH setpoints and environmental trigger points.

In these situations a Batched Dosing System cannot be used as the larger batching tank would take too long to be refilled, dosed, stirred and fed out to each zone. Fertigations would be required in rapid succession during hot periods so this slower turnover time would mean that a batched dosing system would be unable to keep up with demand.

To overcome this problem a more advanced Fertigation controller is used which doses via an inline injection system or turbulent mixing tank system. This enables all of the zones in the greenhouse to be fertigated in rapid succession with no delay time in between.

An injection manifold containing high flow solenoid dosing valves attached to venturi injectors are used to dose the nutrient stock solutions and pH corrector and any other additives into a pressurised line or turbulent mixing tank which is continuously being pumped out to the activated zone.

Inline EC and pH sensors installed downstream of the injection manifold monitor the passing EC and pH strengths and this provides immediate feedback to the Fertigation controller. The controller is then able to immediately adjust the injection ratios to a high level of accuracy. The controllers are also self learning so are able to adjust their performance for the next fertigation cycle.

The advanced Fertigation controllers are able to be operated from a PC, laptop or tablet and can be controlled remotely with data logging and graphical displays.

Please talk to Pure Hydroponics to discuss the best options for your greenhouse system and how to take your standard of growing to the highest level.