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

Fertilization of soils contaminated by radionuclides with potassium (K) and its effect on (137)Cs 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 ((137)Cs) 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, (137)Cs transfer factors in control treatments ranged between 0.0004 m(2) kg(-1) (barley grain on sand soil) and 0.07 m(2) 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 (137)Cs 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 (137)Cs transfer to crops was correlated with (137)Cs:K ratios in plant material. Additional application of zeolite caused a 1.4 reduction of (137)Cs transfer to hay on sand and 1.8-fold reduction on organic rich soil; whereas, application of potash-magnesia and CaO had no effect.