In the control of frosts for crop protection, the technique of applying water has been a traditionally utilized practice. However, there is still a belief among some producers and advisors that they should require up to 3 millimeters per hour (mm/h) of water to effectively protect crops from frosts. In this article, we will explore the evolution of this technique, the research behind current recommendations, and how Tierraverde has optimized this process to make it more efficient and accessible to farmers, and why Low Water Precipitation, with rates around 1mm/h, is the most sustainable and efficient alternative available today.
History and evolution of frost control technique
Since the 1980s, the application of water has been a key strategy to mitigate damage caused by frosts. Initially, it was believed that to control frosts with temperatures down to -5°C, 3 mm/h of water was needed. This amount was based on the use of agricultural or garden sprinklers, which distribute large volumes of water at a constant rate.
The only serious article on this topic is a report by the FAO from 2005, suggesting that between 2.5 and 3.5 mm/h of water is required to protect crops. However, this claim lacks solid foundations or studies that fully support the frost control phenomenon. It is an estimate based on observations, without an exact mathematical formula to model its behavior or effect. Fortunately, today there are technologies available in the market based on water pulse emissions that have allowed a significant reduction in the flow rates required to achieve the control effect.
Reality of water application
Tierraverde has conducted exhaustive research over the years and has concluded that the amount of water required to protect crops can be significantly lower. We have reduced the amount to rates of 1 mm/h, or even less, which has proven to be equally effective and much more viable from an economic and logistical perspective. Installing systems that apply 3 mm/h of water exceeds the investment capacity of most farmers, and additionally, overloads the soil and crops with excessive moisture.
The theory behind the use of 3 mm/h of water is based on the idea of equating the soil heat loss on a clear night with the energy gain from transforming water from liquid to solid. However, this equivalence is incorrect and does not reflect how the frost protection system really works. The protection efficiency is based on several factors, including heat transfer and adequate coverage of the crop.
Optimal water application: effect of coverage and heat transfer
The optimal technique for applying water must consider both the amount and the method of distribution. At Tierraverde, we have implemented systems that apply 1 mm/h of water efficiently, fully covering the crops to maximize heat transfer. This method is not only more effective but also reduces costs and the need for large volumes of water.
The key to effective crop protection against frosts lies in total coverage and efficient heat transfer. By applying small droplets of water covering the entire area, the time these droplets remain in the air is maximized, thereby increasing heat transfer to the atmosphere and providing effective crop protection. The total coverage approach reduces heat loss of the water droplet from focused emitters (one over each tree), optimizing the effect of the energy contained in the water.
Maintenance and continuous operation
To ensure the effectiveness of the system, it is crucial to maintain continuous operation without intermittencies. Intermittency can cause the freezing of water particles in irrigation systems, causing blockages and reducing the effectiveness of protection.
While the 1 mm/h technique is effective for most frosts, in cases of extremely low temperatures (below -5°C), crop damage can occur. Nonetheless, even in these extreme conditions, Tierraverde systems provide significant protection, minimizing damages and improving crop recovery in subsequent seasons.
Conclusions
The myth of 3 mm/h of water for frost control has been debunked by nearly 30 years of research and practice here at Tierraverde. By reducing the amount of water to rates around 1 mm/h, we have not only achieved effective protection but also made this technique more accessible and sustainable for producers. We invite all interested parties to consider our frost protection systems and benefit from our innovations in water management.
