We conducted this study to reduce radioactive cesium in tea plants that had been contaminated eleven or thirteen months earlier. The results obtained were as follows: 1) High-pressure washing was applied to tea leaves, twigs and branches contaminated with radioactive cesium at 7.5MPa of 1,200L/10a. However, no reduction of the amount of radioactive cesium was observed. 2) Tea branches contaminated with radioactive cesium were soaked in 1% acetic acid solution(pH=3.52), 1% sodium chloride solution(pH=6.84),1% sodium hypochlorite solution(pH=8.67) and 1% sodium carbonate solution(pH=10.77) for 5 minutes respectively and they were then washed in water after they had dried. However, no reduction in the amount of radioactive cesium was observed. These results suggested that the radioactive cesium would exist not only on the surface of old tea leaves and branches but also in the innner part of them.
In recent years, trimming and pruning of the canopy of tea plants have been performed every year after the second crop, resulting in the accumulation of large quantities of pruned shoots (litter) in the space between hedges. The nitrogen fertilizer applied in the space between the hedges could not reach the soil easily because of accumulation of this litter, and we believe that it became a factor in the decline in the efficiency of fertilizer application. Therefore, in a tea field in which fertilizer was applied over the accumulated litter in the space between hedges, we analyzed the amount of inorganic nitrogen in the soil and the contribution rate of the nitrogen fertilizer in flush seasons by using the 15N-tracer method, and we investigated the influence of this litter on the fertilizer application efficiency. The amount of inorganic nitrogen in the soil remained low in the tea field, even when ammonium sulfate and rapeseed oil cake were used. The 15N contribution rate of the second flush was 4.8% and the utilization rate of the nitrogen fertilizer in the first and second flush was 3.8%; these values were lower than those in a tea field without litter. Consequently, it was thought that the litter accumulated after trimming and pruning in the space between hedges might have been a factor responsible for the decline in fertilizer application efficiency.
The Japanese green tea cultivar ‘Saitama42’ has characteristic aroma such as the cherr y tree’s leaf. Aroma extract dilution analysis has revealed that 6 odorants namely linalool, 3-methylnonane-2,4-dione, β-damascenone, indole, coumarin and vanilline were the most prevalent odorants in ‘Saitama42’.