The correlation of the radiocaesium concentration of new shoots harvested in 2012 and old leaves, and new shoots harvested in 2011 grown in Kanagawa prefecture

We conducted this study to analyze the correlation between 137Cs concentration of new shoots harvested in the first crop of tea in 2012, and new shoots harvested in the shuto-bancha in 2011 and old leaves harvested at the same time respectively. In the first crop of tea in 2012, the 137Cs concentration of new shoots was related to that of old leaves, and the correlation of the coefficient was 0.663(p<0.01). The Ratio of 137Cs concentration(new shoots/old leaves) was related to the days until harvest of the first crop of tea in 2012, and the correlation coefficient was -0.771(p<0.01). This suggested that the decrease of the ratio of 137Cs concentration was derived from the dilution effect due to growth and development of tea plants. Regression analysis was performed to forecast the 137Cs concentration of the new shoots in the first crop of tea. The 137Cs concentration of new shoots in the harvested first crop of tea(Y) was related to the 137Cs concentration of old leaves harvested the previous winter(X). The correlation of the coefficient was 0.783(p<0.05), and the coefficient of determination was 0.558, and the regression formula was Y=0.591X+28.035. Furthermore, the 137Cs concentration of new shoots of the first crop of tea in 2012 decreased about 1/6 to 1/25 compared with that of new shoots of the first crop of tea in 2011. (author)