Evaluation of Cs and Sr accumulation by feed plants: Comparison of field and agar cultivation with addition of stable Cs and Sr

To investigate the environmental dynamics of radioactive cesium (Cs) and strontium (Sr) in farmland in Japan, non-radioactive Cs and Sr were added to field plots and their absorption by pasture crops was examined. The intrinsic Cs absorption capacity of plants was also examined by cultivating them in agar to exclude the possibility of Cs adhering to soil particles. In the field experiment, crop yields decreased when Cs and Sr were added together but did not change significantly when Cs or Sr alone was added. Addition of Cs to the field plot resulted in significantly higher Cs concentration in the crop, while addition of Sr had no such effect. The amount of Cs accumulated by the crop, however, was less than 1% of the amount added to the plot, suggesting that only a limited amount of radioactive Cs from fallout would be translocated to the crop. The agar cultivation test revealed a positive correlation between the growth rate and the Cs content of the crop. The Cs concentration in plants cultivated in agar was closely correlated with that in the field crop. This suggested that Cs absorbed by plants in farmland remained in a free state because K and Ca in soil inhibited its adhesion to soil particles. In conclusion, it was considered that almost all Cs in farmland adhered to soil particles and was not available for adsorption by plants, while a small portion remained in a free, absorbable state due to the effects of nutrient elements.