Abstract:Confronted with severe frost damage to plants, methods, technologies and equipment have been developed and applied during the past century. The paper presents a comprehensive review on the most effective and active technology to protect plants from radiation frost based on air disturbance technology. The working principle of the technology was elaborated with frost protection mechanism, structures and applicability of three types of working patterns: conventional wind machines, selective inverted sink and portable vertical blowing. As an automatic mechanized technology, control strategy, applicable occasion and proper parameters are introduced for each type of working pattern. The operation of the technology and equipment depends on plant critical temperature, prevailing climatic conditions, thermal inversions strength, as well as costs. The frost protection performance and effectiveness of conventional horizontal wind machines, selective inverted sinks and helicopters are discussed and compared from the cost-effectiveness and application aspects, and the feasibility of selective inverted sinks is still controversial. Therefore, conventional wind machines are the best choice for plant frost protection and consequently are widely used in temperate and subtropical areas throughout the world. The frost protection application with helicopters is not easy to use during the frost nights with high cost. The paper also provides researchers with some perspectives on improving air disturbance technology and its equipment, and some practice recommendations for growers.

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Abstract. To validate the feasibility of an automated frost protection sprinkler system, a sprinkler irrigation system with an optimal water application rate was designed, constructed, and tested in a tea field. A modified calculation model of the water application rate was provided by simulation with different values of airflow velocity, air temperature, air humidity, and spray water temperature. An intermittent control strategy was provided using a modified model that included the start and stop time of the system and adjustment of the water application rate. Tea field experiments were conducted to evaluate the effect of frost protection based on this control strategy during frost night events. The results showed that a variable water application rate was better suited for frost protection, and the modified intermittent control automatically regulated the water application rate. In early spring and winter heavy frost nights, the canopy temperature (Tc) of the irrigated area remained above -1.2°C and 0°C, respectively, which is higher than the critical damage temperature for tea plants. The Tc of the irrigated area was approximately 2.8°C higher than that of a non-irrigated area. Moreover, the irrigated area with the modified model had a slower temperature rise after sunrise compared with the non-irrigated area, which was beneficial for frost protection. This sprinkler control strategy is an effective frost protection method that could be applied for in tea fields in the Yangtze River region. The calculation and simulation procedure of the water application rate would be applied for constructing sprinklers for different micrometeorological environments. Keywords: Frost protection, Intermittent control, Spraying water temperature, Sprinkler irrigation system, Tea, Water application rate.