Potassium fertilization and 137Cs transfer from soil to grass and barley in Sweden after the Chernobyl fallout

•K application on sand and peat soils was effective at 50–100 kg ha−1 level.•200 kg K ha−1 caused 4–5-fold reductions in 137Cs transfer for hay and barley.•Effects of K application were greater on sand than peat soil.•Reduction in 137Cs transfer from soil to crops was observed in the first cut.•Application of zeolite was effective, but potash-magnesia and CaO had no effect.

Fertilization of soils contaminated by radionuclides with potassium (K) and its effect on 137Cs transfer from soil to crops is well studied in field conditions; however experiments over many years are few.The effects of potassium fertilization on cesium-137 (137Cs) transfer to hay, pasture grass, and barley growing on organic rich soils and mineral sand and loam soils in a number of field experimental sites situated in different environments in Sweden are summarized and discussed. The basic experimental treatments were control (no K fertilizers were applied), 50, 100, and 200 kg K ha−1. In the experiment, which lasted over 3–6 years, 137Cs transfer factors in control treatments ranged between 0.0004 m2 kg−1 (barley grain on sand soil) and 0.07 m2 kg−1 (pasture grass on organic rich soil). Potassium application on soils with low clay content i.e. mineral sand and organic rich soils was effective at the 50–100 kg ha−1 level. Application of 200 kg K ha−1 resulted in a five-fold reduction in 137Cs transfer for hay and up to four-fold for barley grain. The effects of potassium application were generally greater on sand than organic rich soil and were observed already in the first cut. After K application, the reduction in 137Cs transfer to crops was correlated with 137Cs:K ratios in plant material. Additional application of zeolite caused a 1.4 reduction of 137Cs transfer to hay on sand and 1.8-fold reduction on organic rich soil; whereas, application of potash-magnesia and CaO had no effect.