Optimize growing conditions with high-pressure fogging in strawberry propagation and production
Rob Kwinten makes a good case for the MJ-Tech high-pressure fogging system that cools down the greenhouse crop during different growing seasons. As the Business Development Manager of the companies MJ-Tech, Growtec, and Robur, he presented at the Grand Opening Event of EZ Grow Farms, a strawberry propagation and growing facility, in Langton, Ontario, in late June 2024.
A key observation is how this high-pressure fogging system is combined with other growing parameters; such as ventilation, screening, and CO2 dosage.
Photo caption: Rob Kwinten giving a presentation at the EZ Grow Farms event, in Langton, Ontario, and an active nozzle from the MJ-Tech high-pressure fogging system.
The implementation of high-pressure fogging creates adiabatic cooling, which occurs when air is cooled by spraying very small droplets of water into it. As the water evaporates, it increases the latent heat of the air. This process removes energy from the air, reducing its temperature and decreasing the sensible heat by an equivalent amount, while keeping the enthalpy unchanged.
High-pressure fogging promotes a balanced water uptake, thereby keeping stomata open for both photosynthesis and transpiration. Consequently, both air and plant temperature decrease. This combination of increased humidity and decreased temperature improves water use efficiency, avoids water stress, and enhances photosynthesis. And will allow to reduce screening hours in warm periods due to the lower greenhouse and plant temperature.
It is important to ensure that the moisture evaporates before reaching the plants, thus minimizing the risk of promoting diseases, achieved by using small droplet sizes and determining the right start and stop time of the high-pressure fogging unit based on solar radiation (W/m2) and humidity deficit level (g/m3). Nevertheless, other risks can occur. For example, if the grower starts fogging too early, that can lead to tip burn.
Controlling the ventilation rate is crucial to maintaining the perfect balance between greenhouse temperature and humidity. As humidity levels rise, the enthalpy of the greenhouse increases, allowing for a reduction in ventilation rates. This reduces CO2 losses and helps maintain higher CO2 concentrations inside the greenhouse, optimizing photosynthesis.
To optimize misting control, sensors should be installed to monitor solar radiation, plant/leaf temperature, water uptake, air temperature, and relative humidity, enabling precise adjustment of misting setpoints in different climate conditions, greenhouse set-ups, seasons, plant types, and planting dates.
High-pressure fogging is beneficial after planting in August/September, as it will create a vegetative climate. That will contribute to creating a well-formed root system from the start.
Temperature control over the 24 hours of a day is critical. If the 24-hour temperature is too high, the fruit size will decrease, and irregular-shaped fruit will occur. Ensure that day temperatures are controlled so that fruit size and weight are well classed, and to keep the fruit load in balance.
Another important benefit of the fogging that was found in research is the IPM. In a greenhouse microclimate, IPM management has never been more important. Beneficials are more effective when the ratio of temperature and humidity are in balance. For example, Phytoseiulus is a predator of spider mites. This species is most effective in a temperature range of 21-27°C. Creating a stable climate with high-pressure fogging will allow better development, and higher hatching and survival rates, which will result in higher population and efficiency of the beneficials.
EZ Grow Farms has installed a high-pressure fogging system to create a vegetative climate for stable tip production. Starting the propagation phase fogging is used to stimulate root growth and the settings are adjusted when the tips are well rooted.
Last but not least, the use of a high-pressure fogging system creates a more comfortable working environment, not only for the plants but for the employees as well. That is also important, especially during heatwaves or warm summer days, allowing the workers to safely complete their tasks and maintain high work efficiency.
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Copyright The Grower, By Karen Davidson
August 2024 | Volume 74 Number 08 https://thegrower.org/archives
