The Actual Survey of Frost Injury on the Tea Field in the Spring 1972

Abstract

1. In the spring 1972, the frost injury in the tea field was very severe and it covered wide areas. We carried out an actual survey on the influence on the shoot growth, yield and the price of tea after the injury, and the effects of several preventive measures were researched as occured.2. The frost injury occured all over the country, especially on 2nd, 3rd and 10th April and 3rd May. And the minimum air temprature was -6.0°C at Miyazaki and Nagano prefecture. Therefore, the plucking time of first crop was delayed and the yield of tea was decreased everywhere, accordingly the earning was decreased though the price of tea was dear slightly.3. The degree of injury differed with the condition of locality and the type of cultivation in the tea field. But the relations between these conditions and the injury did not differ when compared with previous survey.4. On the preventive measure of the frost injury in the tea field, the protection methods by covering, heating and fog were adopted from old times, but in addition to these methods the protections by the wind machines and the application of water were used.As the frost protection by covering was effective, the practice of using chemical fibre cloth for protection became more extensive. But when the air temperature was dropped extremely the effect was not perfect though the growth of new shoots after the injury was more rapid than non-covering ones. The protections by the wind machines and the application of water were effective, but they had some doubtful points to the practical use. The protections by heating and fog were not effective.