Technologies for Improved Greenhouse Tunnel Management.

Increasingly challenging weather patterns combined with increased demand from markets has resulted in many open-field producers moving to production under cover – be it Shade net or polythene.

While there is no doubt about the myriad advantages of producing under cover, these structures do come with associated management challenges, mostly centred around fertigation and the management of the micro climate that the structure provides.

If these are not correctly managed, disease, pests and deficiencies can mitigate all of the potential gains resulting in heavy financial blows to the grower.

Fortunately, though, technology is available to help even the novice undercover grower.

We will take a brief look at some of these, by breaking them down into two sections namely Fertigation and Climate control, with the aim of promoting awareness of the tools available.  For more in-depth information, feel free to contact Haygrove and speak to our consultants in this regard.

Fertigation – this includes irrigation as well as nutrient provision through the irrigation water. (Hydroponics)  The most common system in use is substrate in pots, where plants are fed salt-based nutrients though a drip irrigation system.  The challenge here is to supply enough water and nutrients at the correct times, without a build-up of salts in the substrate.  The limited growth media volume makes this a tricky balancing act.  It is essential to know what the moisture content, as well as the EC (Electro conductivity) of the growth media is, throughout the day, in order to provide for the plants water and nutrient needs, as well as to ensure there is sufficient flushing of the substrate.

Combined ph and ec meter
Combined ph and ec meter

 

Tools available for this are:

  • Handheld moisture meters
  • Ph meters (Hand held or continuous logging)
  • EC meters (Hand held or continuous logging)
  • Capacitance probes (Continous logging)
Handheld probe
Handheld probe

 

Handheld instruments are handy for spot checks and are generally quite cheap.  Used correctly and with good records kept, they are a powerful tool.  However, they require discipline and the data needs to be manually analysed, which can be challenging in a larger production unit.

Continuous loggers, while more expensive, have the benefit of being linked to software and/or mobile apps that are able to analyse the data and provide growers with instant alarms based on predetermined parameters.  They can also be linked to irrigation timers and fertilizer dosing pumps in order to automatically make changes.  Another benefit is the building of history and various analytical report functions available from many of the apps or software packages.  Many of these packages are cloud-based and are accessible anywhere at any time.  Capacitance moisture probes can also measure moisture (and often also EC) content at various depths within the pot which makes the particularly useful, both for fertigation and disease management.

 

 

Capacitane Probe
Capacitane Probe

 

 

Climate Control – this encompasses the processes to manage and manipulate the micro-climate in the greenhouse.  The most important data here is air temperature (both inside and outside), leaf temperature, Relative humidity and dew point temperature inside the tunnel.  This set of data is used to ensure correct and adequate venting as well as to manage disease.  Inadequate or incorrect venting is often the cause of many of the problems associated with greenhouse tunnels, and is one of the least understood principles – possibly because it is an alien concept to open-field growers.

Tools available to assist are:

  • Weather station (an almost indispensable tool in any larger production unit)
  • Temperature sensors inside the structures. (Continuous logging and linked to station)
  • Humidity sensors. (Handheld or Continuous logging
  • Infrared temperature sensors to measure leaf temperature. (Handheld or continuous)
  • Pocket weather stations (Eg Kestrel 3000) which can provide multiple data sets such as Temp/hum/wind/dew point temperature
Kestrel- 3000
Kestrel- 3000
Weather Station
Weather Station

 

Once again, handheld instruments are cheaper and are quite user friendly as well as having the advantage of being able to be used on multiple sites.  Many of the better weather stations can be linked to wireless temp/humidity sensors inside the greenhouse and can also be linked to weather software able to provide analytic reports and keep weather history.  These apps are available for viewing from any smart device or computer.  Alarms can be sent to the grower or his managers, warning of danger conditions such as excessive heat, high winds, heavy rain or excessive humidity, enabling swift action to be taken.  Likewise, forecasts for weather and disease conditions are available from many of the better systems.  Forecasts can also be used for planning spraying days and help in irrigation scheduling.

With the correct applicable technology, the growers level of management can be greatly enhanced and he is able to react proactively as opposed to reactively.  Costly mistakes can be avoided and both yields and produce quality can be improved.  It must be borne in mind though, that data by itself is useless.  The power lies in interpreting the data and reacting to those interpretations.