Studies on the Root Rot Disorder of Tea (Part 3): On the Root Development, Deterioration of the Rootlet with Regard to the Physical Properties of Soils in the "Root Rot Disorder" Tea Fields

Physical properties of soil, distribution and deterioration of rootlet were investigated in 11 tea fields which had various extent of damage of the root rot disorder in Shizuoka and Aichi Ken. The 11 tea fields were divided into following three groups according to the state of root rot and the probable causal agents. Group 1. In 4 fields, some inferior physical properties of soil were seemed to be mainly concerned in the disorder. In such tea fields, the soil had smaller air phase and the root development was poor or only seen near soil surface. Group 2. In 3 fields, "Tenchigaeshi" (turning over the soil about I m. depth) before planting might be pointed out as one of the most important cause of the disorder. As the unfavorable underlayer soil was exposed to near surface by this treatment, the root growth was generally repressed. Group 3. In 4 fields, other factors except soil physical properties, such as microbial, nutritional and other agents might be concerned in this disorder. In these tea fields, much rotted roots were usually observed. Among these 3 groups, tea field belonging to group 3 only showed some disease-like aspects of this disorder.