Frost Prevention

Frost prevention is only one of the headaches of the modern farmer.  Farmers have a constant battle against the elements in ever-changing weather patterns.  Too much rain, then too little rain and now more frequent than ever frost problems.  In an article by Landbouweekblad’s Tegnologie No 2 of 2021 a vineyard farmer in the Cederberg area described a growing dilemma during winter.  In more consecutive seasons his vineyards are becoming vulnerable to frost damage.  It is comprehended that frost conditions could occur every few years and farmers can plan for that occurrence.  As soon as it becomes more regular, plants cannot recuperate enough to produce an optimum yield when conditions are good.

It is a well-known fact that cold air will settle at the lowest points of a farm and if conditions are below dew point, freezing of plant cells will occur, known as frost damage.  Warmer air can be found in layers a few meters above the ground.  As a young engineer the development of an air blower sucking warmer air from the upper layers of the farm and exhausting above the plants as frost prevention was on the drawing table.  A South African company has gone one further and produces fan units at height of 10m above ground. That prevents the forming of cold layers of air close to the ground, with excellent success preventing frost damaging to multi-year plants, according to the farmer.

The same frost prevention opportunities are found with other sensitive plants, as with dragon fruit production.  The farmer can lose his entire crop is one week of severe cold conditions.

Internet of Things (IoT)

With the introduction of IoT it is now possible to have a great number of sensors communicating to a single gateway over a long distance.  The development of LoRa communication protocol enables a sensor to communicate wireless over distances of two to five kilometres in line of sight.  The sensors are battery powered with an expected battery life of 2 to 15 years, depending of the frequency of sending data packages.  Communication is not a new concept with telemetry, PLC’s and SCADA the current tools, but LoRa (short for Long Range) is the new protocol making wireless communication possible.

In this application of frost prevention during winter it is possible to roll out a number of ambient temperature (and humidity) sensors across the field.  It is then possible to send data from all sensors to a screen (or cell phone).  The farmer can cover as much of the land as he requires, selectively placing one sensor closely above the plant and another sensor 10 to 15m above the plant.  Temperature information can be displayed in real time and only alerts and exception sent to various cell phones.

Additional to monitoring, LoRaWAN makes it possible to control the fans.  Fans can be activated automatically from a LoRaWAN output when conditions are below the dewpoint, and frost be expected.  The fans already on the market are driven by a solar powered battery.  To give the farmer additional assurance that the fans are active when necessary it should also be monitored.  Sensors can be added to the equipment to monitor fan movement (vibration) and read available battery voltage to last the night.  Everything to the same network.

Technology is a game changer

It is not possible to look after your crop day and night without technology.  The software (rules engine) of the LoRaWAN network enables the farmer to be alerted and ever woken at night by setting off an alarm when necessary.  If you have a cellular phone, you can be alerted anywhere in the country.  The following is a schematic diagram of the four levels of a typical LoRaWAN network:

LoRa Network
Simplified LoRa network

Service Provider

Omicron IoT is a service provider that can assist farmers to set up a LoRaWAN network to monitor and reduce losses using the latest technology.  The network can be expanded to include soil humidity, pump control, dam levels and even security measures to the same platform.  The agricultural engineer has more than 20 years’ experience in asset management, and can be contacted here.


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