Late frosts: an entire agricultural year ruined in a few hours

Late frosts are unforgiving and, within a short time, can cause severe damage to crops, even permanent in the case of woody plants, resulting in significant yield losses. Unfortunately, with climate change, these events have become increasingly frequent. Is it possible to defend against them? How to protect plants? Let's discover together old and new tools available to farmers.

Let's start with the basics: a frost can be defined as a sudden drop in air temperature below zero degrees Celsius prolonged over several hours. The adjective late indicates that the frost occurs at a time of year when it should not occur, or at any rate is rare to occur.

Why do frosts occur?

Frosts are weather events that can be caused by several factors, hence the classification into:

• Advection frosts: are caused by thearrival of cold air masses that cause the temperature to drop below zero degrees Celsius. Specifically, we speak of synoptic advection if the cold air mass arrives from northeastern Europe and local frosts if the frost is caused by the descent of cold air from a mountainous or hilly relief.

• Radiation frosts: these are caused by the loss of heat (and thus cooling) from the ground and the consequent cooling of the air in contact with it. The drier and stiller the air is, the more it will cool: this is precisely why they are favored by clear, windless days.

• Mixed frosts: are frosts whose causes may be a combination of advection and radiation.  

Are frosts a problem for agriculture?

Not per se, as long as they occur during the plant's vegetative rest, thus during the purely winter months. Plants have developed various defense systems against low temperatures, such as increasing the salt concentration of intracellular fluids, thereby lowering their freezing temperature. This phenomenon is called cryoscopic lowering and is the same rationale for throwing salt on roads when there is ice.

What if the frosts are "late"?

The real problem in agriculture is not frosts themselves, but late frosts, as they occur at a time of year, typically spring, when the plant has already resumed vegetation. In these cases it will not have defense mechanisms in place, and subzero temperatures can cause intracellular water to freeze, causing its volume to increase and cell membranes to rupture. Late frosts, if severe, can literally wipe out the entire crop year's production and, in the worst cases, compromise the health of the plant.

How to solve the problem?

Since weather is an impossible entity to control, the key word is prevention. There are several methods used in agriculture to defend one's crops from late frost, and if activated early, they can literally save the year:

• Encender fuegos o antorchas antifrost a lo largo de las filas de cultivos para calentar el aire. No es la solución más cómoda ni sostenible, pero sí una de las más visualmente impactantes.

• Use of fans to promote air recirculation and thus prevent it from lingering on the surface of the ground favoring its lowering of temperature.

• Riego antiheladas, que consiste en rociar agua sobre las plantas durante toda la helada. Al congelarse, el agua libera calor latente y mantiene la temperatura en 0 °C, protegiendo los tejidos de la planta.

How can xFarm help prevent late frosts?

xFarm can help predict when frost will occur, allowing the aforementioned protective methods to be activated in time.

Thanks to the Alerts Module in the app, it is also possible to set up custom notifications that can alert you when certain conditions occur. For example, an alert can be set to go off when the temperature drops below zero degrees for more than two hours, sending a text message alerting you of the situation in real time. In this way, you can take timely action to protect your crops with mitigation strategies.  

Sensors that can be used to collect the data on which alerts are based include the classic weather station, but especially the sensor for measuring wet bulb temperature. This parameter is particularly useful for predicting frost because it provides a more accurate indication of the actual temperature that an exposed surface, such as soil or crops, may reach.

Finally, the Agrometeor Module provides accurate forecasts, which help to understand when frosts will strike and to put preventive measures in place.

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