Assessment of phytoavailability of Sr in an Andosol by addition of stable isotope

Abstract

Time-dependent changes of phytoavailability of Sr after adding it to the soil were studied for better prediction of radioactive Sr behavior in soil–plant systems. Strontium-86 enriched stable isotope was added to a soil sample collected from a field of humus-rich Andosol. Plant uptake and extractability of Sr in the soil were assessed at given times after the addition during a 12-month period including repeated drying-rewetting. Proportion of the added Sr extracted by 1 M ammonium acetate solution from the soil was 45–58% throughout the period, which corresponded to that of long-time aged 90Sr in the soil. Pot cultivations of orchardgrass (Dactylis glomerata) and red clover (Trifolium pratense) were carried out starting with uncropped soil for four weeks five times during the experiment. Clear time-dependent changes were not observed in uptake of the added Sr by the plants. Aging is unlikely to decrease Sr availability over time. The labile form of Sr determined with the isotopic dilution method was approximately 15% of total soil Sr, and more than the percentage of the extractable Sr in the soil. The results suggest that a part of the non-extractable forms of Sr in the soil would be available to the plant.