Vertical distribution of Cs-137 in cultivated chernozems of the Plavsk radioactive hotspot has been investigated, with the emphasis on the plough horizon. It is shown that the commonly expected complete homogeneity of the isotope vertical distribution within the plough and old-plough horizons of cultivated chernozems is not always achieved. Incomplete homogeneity can be explained by the application of different cultivation techniques for various crops within the crop rotation system employed. Important observation is that in cases of relatively shallow cultivation (such as disking to 12-15 cm depth) the largest root biomass content remains within the upper 10 cm layer, while maximum Cs-137 content is shifted downwards to underplough layer at 10-20 cm depths. At the same time, traditional cultivation with plough layer rotation and mixing to the 20-25 cm depth results in more uniform Cs-137 distribution through the plough layer, while layer of active root uptake of mineral matter for row crops shifts from the soil surface downward. Therefore, it can be recommended that the systematic monitoring of cultivated topsoil conditions based on preliminary assessment of Cs-137 vertical profile distribution, taking into account agrotechnical specifics of different crops within the crop rotation, must be carried out in order to obtain the reliable assessment of the soil radioecological status.

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