Potassium fertilisation reduces radiocesium uptake by Japanese cypress seedlings grown in a stand contaminated by the Fukushima Daiichi nuclear accident

Masabumi Komatsu,Junko Nagakura,Keizo Hirai,Kyotaro Noguchi

doi:10.1038/s41598-017-15401-w

Masabumi Komatsu, Junko Nagakura + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-15401-w

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Abstract

We analysed suppressive effects of potassium (K) fertilisation on radiocesium (137Cs) uptake by hinoki cypress (Chamaecyparis obtusa) seedlings from soils contaminated after the Fukushima Daiichi Nuclear Power Plant accident. Three-year-old seedlings were planted in a clear-cut forest (ca. 4 ha) during June–July 2014, and potassium chloride fertiliser (83 kg K ha−1) was applied twice (August 2014 and April 2015). 137Cs concentrations in the needles in the fertilised plots were one-eighth of those in the control (unfertilised) plots at the end of the second growing season (October 2015). Our results clearly indicated that K fertilisation reduced radiocesium transfer from soil to planted cypress seedlings. A linear mixed model analysis revealed that 137Cs concentrations in the needles were significantly affected by 137Cs inventory in the soil (Bq m−2) adjacent to the sampled seedlings, exchangeable K concentrations in surface mineral soils (0–5 cm) and fertilisation. The exchangeable K concentrations in surface soils in October 2015 did not differ from those in August 2014 (before fertilisation) in the fertilised plots and in the control plots. These results suggested that the levels of exchangeable K would temporarily increase by fertilisation during the growing season, and radiocesium uptake by tree roots was suppressed.

Highlights

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident following the large earthquake on 11 March 2011, large areas of forest lands, as well as other lands, were contaminated with the released radionuclides around the coastal and central areas of Fukushima prefecture
It has been reported that K fertilisation in paddy fields and farmlands reduced radiocesium transfer to rice and other crop plants growing on the soil contaminated by the FDNPP accident[13,14]
The exchangeable K concentrations in surface soils in October 2015 did not differ from those obtained in August 2014

Summary

Introduction

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident following the large earthquake on 11 March 2011, large areas of forest lands, as well as other lands, were contaminated with the released radionuclides around the coastal and central areas of Fukushima prefecture. The transfer of radiocesium to the trees planted by afforestation after the accident has not been well studied, despite such information being indispensable to discuss future availability of wood and forest resources. We define the total soil 137Cs inventory as sum of 137Cs inventory of organic layer and that of mineral soil from 0 cm to 20 cm depth Such Tag concept intends that the radiocesium transfer to trees would be usually controlled by radiocesium absorption from soils via roots. It has been reported that K fertilisation in paddy fields and farmlands reduced radiocesium transfer to rice and other crop plants growing on the soil contaminated by the FDNPP accident[13,14]

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