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Effects of irrigation in the tea field was investigated for 4 years from 1974 to 1977 by using intercept apparatus of the rain.Amount of 15 mm, 20mm, 25 mm and 30 mm were irrigated when pF at a depth of 15 mm in the plot of 30mm attained 2.8 (1975) or 2.5 (1976 -'77).The yield of green leaf was the following order;30mm>25mm>20mm>15mm plot.Irrigation had little effect on the lst crop of green leaf, but had an effect on the 2nd and 3rd crop of green leaf.For the number of buds there was no difference among treatments at lst crop, but at the 2nd and 3rd crop of green leaf, the more amount of watering was, the more number of buds was.The weight of bud was the same as the case of the number of buds.Evapo-transpiration of tea plant was about 2mm per a day in March and April, 2-3mm in May-July, 5-6mm in Auggust and 2-3 mm in September-October. respectively.Evapo-transpiration decreased according as value of pF increased.Evapo-transpiration of tea plant was related to climatic factors and showed the high co relation to solar radiation, sunshine duration, air temperature and evaporation, Soil moisture in March-July was extractedmainly from upper layer and in August-October mainly from lower layer.From the results of soil moisture extraction, amount of irrigation and yield of green leaf, it was considered suitable that the volume of TRAM was irrigated at pF 2.3 in the tea field.

It has been recognized in. many experiments that the grass mulch has remarkable effects on the tea field. But optimum quantity of grass for mulch has not been yet well known.This experiment was carried out to determine the optimum quantity of the grass mulch for the tea field.The results obtained are as follows;1.In the mulchless tea field on slope, the growth of shoot, the yield of green leaf and the quality of green tea were inferior to those in the mulch field. This was thought to be mainly induced by deterioration of micro climate and run-off of fertilizer.2.The optimum quantity of grass mulch will be fluctuated by the kinds of grass and tea soil, but in this experiment, it was determined to be 10 ton fresh grass per hectare. The growth of shoot, the yield of green leaf and the quality of green tea were good at this quantity. Therefore the grass mulch was thought to be suitable for management of the tea field.

1. In order to clear the actual condition of tamaryokutya for export, the qualities and chemical constituents of three China crude teas, five Japan refined teas, three Viet-Nam crude teas and five Japan crude teas (made in this Station) were investigated.2. The qualities of these samples were examined by ordinary method of testing, and it was recognized that Japan teas generally had green color and thin liquor and taste compared with China and Viet-Nam teas.3. Concerning with the chemical constituents of these samples, total-N. had no distinct difference among them. except Japan gun-powder and chum-mee of Shiro Brand, but soluble N. tannin and hot water extract were richer in Viet-Nam teas and crude ash and alkalinity of ash were poorer in Japan teas than in others.4. On the relation of qualities of Yonkontya and content of pectin and total-N. significant correlations existed between the ranking of liquor, aroma and teste by sensory test and total pectin, and between the ranking of appearance and aroma by sensory test and total-N. respectively, but it seemed that further examination was needs on the results of total pectin.5. Although Japan refined teas for export were more improved since the late survey, it was necessary to pluck tea leaf on younger stage, and to improve the qualities of green leaf itself.

1. In order to establish the suitable manufacturing procedure of several tea varieties for Sentya, the characteristics of sentya made with eleven varieties as well as the behaviour of these varieties in the manufacturing process were investigated from 1949 to 1958.2. It was recognized that these varieties could be separated into two groups, one type of which showed much more excellent quality on the first crop than the second and third crop, but other type had no remarkable difference among each. season, and four varieties of Yabukita, Asatsuyu, S6, U9 which belonged to the former type had superior quality for sentya.3. The color of green leaf which was indicated by B/R of Lovibond Tintometer was closely correlated to the ranking of tea color by the sensory test, but B/R did not show the specific tone of tea color.4. A high correlation existed between total nitrogen and sensory estimation of qualities of tea, and between soluble nitrogen and (sensory estimation of tea) taste respectively.5. Concerning with the behaviour of these varieties in steaming process and primary heating and rolling process, the loss of weight of tea leaves after the primary heating and rolling process affected the qualities of tea on the case of four varieties of Yabukita, U9, Tamamidori, S 6, but steaming period had no relation to the quality of tea except one variety of S 6, 6. As the investigation of these eleven varieties ended except the examination of manufacturing process, this research will be continued with newly selected varieties on the characteristics of sentya manufactured from each variety.

The plucking time can be delayed one or two weeks by some chemicals in each season, as reported bfore, so the yield (green leaf) and quality of tea were examined according to the length of delayed period.As the chemical spraying in the first season can not keep its effectiveness in the second season, it is necessary to spray some chemicals in the second one to retard the growth of shoot.By this delaying method, the yield may be expected to increase in the first season, but has a tendency to decrease in the second season.And generally the later the plucking, time in the third season, the less the growth in the next year, but the number of shoot increases somewhat, so the yield can not be expected to decrease, so it is unprofitable to delay the growth extremely in the third season.The quality of tea can not be effected so remarkably in this test.So it will be favourable to apply this method in the plucking program in order to regulate the plucking time.