Continuous N fertilization immobilized nuclear accident-derived ¹³⁷Cs in apple orchard soil during 10 years after the accident

For 10 years after the 2011 Fukushima Daiichi Nuclear Power Plant accident, we monitored the effects of long-term nitrogen (N) fertilization (up to 20 g N m^‑2 year^-1 since 1973) of apple orchard soil on the vertical migration of cesium-137 (¹³⁷Cs) released during the accident.
At 5 years, the vertical migration rate of ¹³⁷Cs was significantly lower in an N-fertilized plot (N plot; 0.42 cm year^-1) than in an unfertilized plot (0N plot; 0.77 cm year^-1). The upper 2 cm of soil retained more ¹³⁷Cs in the N plot (69% of the total in the upper 10 cm) than in the 0N plot (19.5%). At 10 years, the vertical migration rate was still significantly lower in the N plot (0.34 cm year^-1) than in the 0N plot (0.43 cm year^-1). The upper 4 cm of soil retained more ¹³⁷Cs in the N plot (75%) than in the 0N plot (49.8%). At both 5 and 10 years, the amounts of exchangeable ¹³⁷Cs as a percentage of the total ¹³⁷Cs at the corresponding depth in each year were significantly lower in the N plot (0.64-0.87% at 5 years, 0.37-0.91% at 10 years) than in the 0N plot (4.5-5.2% at 5 years, 2.3-3.2% at 10 years). The amounts of oxidizable organic-bound ¹³⁷Cs as a percentage of the total ¹³⁷Cs were significantly lower in the N plot (4.5% at 5 years, 1.8-2.2% at 10 years) than in the 0N plot (7.1% at 5 years, 4.1-5.0% at 10 years). At 10 years, the amount of ¹³⁷Cs in the aboveground biomass of groundcover grasses was positively correlated with the amount of exchangeable ¹³⁷Cs in the upper 5 cm of soil (P=0.065). Overall, long-term N fertilization reduced the vertical migration of ¹³⁷Cs in soil and its uptake by groundcover grasses by immobilizing ¹³⁷Cs in the surface soil.

IV Asian Horticultural Congress – AHC2023

K. Matsuoka, M. Igura, N. Moritsuka, T. Anazawa

apple tree, ¹³⁷Cs form, Fukushima Daiichi Nuclear Power Plant accident, soil ¹³⁷Cs, vertical migration

https://doi.org/10.17660/ActaHortic.2024.1404.27