Effectiveness of medium pruning on the reduction of radioactive cesium concentration in new shoots of tea plants in Ibaraki Prefecture, Japan

Figures & data

Figure 1 Changes in radioactive cesium (Cs) concentration in new shoots of tea plants.

All samples were periodically collected from 16-year-old (in 2011) tea plants (Camellia sinensis cv. ‘Yabukita’). The bar on July 26, 2013, shows only ¹³⁷Cs, because ¹³⁴Cs was not detected in the sample (< 4.0 Bq kg⁻¹ fresh weight). Error bars indicate ± standard error.

Table 1 Effect of medium pruning and conventional skiffing management on raw leaf yield, the number of new shoots and radioactive cesium (Cs) concentrations in new shoots of 9-year-old (in 2011) tea plants (Camellia sinensis cv. ‘Yabukita’)

					Radioactive Cs concentraion in new shoots of tea plants
Date and type of management	Raw leaf yield (g fresh weight m^–^2)		Number of new shoots (number m^–^2)		(Bq m^–^2)		(Bq kg^–^1 fresh weight)		Index ^b
July 14, 2011 (second tea crop)
Conventional skiffing management ^a	255		−		24.9		176.0		−
May 31, 2012 (first tea crop)
Medium pruning ^a	154		161		2.6		17.0		76
		*		*		*		ns
Conventional skiffing management	322		394		7.2		22.4		100
May 26, 2013 (first tea crop)
Medium pruning	205		470		1.1		5.2		75
		*		*		ns		ns
Conventional skiffing management	233		728		1.6		7.0		100

Plants in both plots were under conventional skiffing management after June 9, 2011. Both plots were n = 3, except for the plot under conventional skiffing management that was n = 2 on July 14, 2011. The significance of the difference between the treatments was examined with Student’s t-test (*: p < 0.05; ns: not significant).

^a Medium pruning: approximately 40 cm from the ground after the first tea crop on June 8, 2011, 3 months after the nuclear disaster.

^b Radioactive Cs concentration in new shoots under medium pruning compared to those under conventional skiffing management (100).