Effects of the simultaneous application of potassium and calcium on the soil-to-Chinese cabbage transfer of radiocesium and radiostrontium

Pot experiments were carried out in a greenhouse to investigate how effectively the transfer of radiocesium and radiostrontium from soil to Chinese cabbage could be reduced by applying K and Ca simultaneously to the soil. The sources of these elements were KCl and Ca(OH)2 at agrochemical grades. Varying dosages of K and Ca were tested for an acid loamy soil treated with a mixed solution of 137Cs and 85Sr at two different times - 3 d before sowing and 32 d after sowing. For the pre-sowing deposition, the soil-to-plant transfer of 137Cs decreased sharply with increasing dosages of K and Ca (K/Ca, g m−2) from 4.8/46 up to 22.4/215 but the 85Sr transfer had the greatest reduction at a dosage of 12.8/123. At this dosage, an about 60% reduction occurred for each radionuclide. Plant growth was inhibited from the dosage of 22.4/215, above which all the plants died young. Both dosages of 4.8/46 and 12.8/123 tested following the growing-time deposition produced around 95% reductions for 137Cs and 50% reductions for 85Sr. In the second year after the 12.8/123 applications, the effects for 85Sr were almost the same as in the first year, whereas those for 137Cs were diminished slightly for the pre-sowing deposition and markedly for the growing-time deposition. Considerably (K) or slightly (Ca) higher doses than 12.8/123 would be allowable for the maximum TF reductions achievable without a growth inhibition.