ASSESSMENT of contamination of man's food chain by strontium-90 through plants is complicated by variables in the plant's source of this isotope. Thus the content of strontium-90 in plants from fall-out may be influenced by foliar absorption1, stem-base absorption2, and the vertical distribution of strontium-90 in the soil profile3. In cultivated soils, the low mobility of strontium-90 coupled with normal tillage practices eventually will lead to a relatively uniform distribution of strontium-90 within the rhizosphere. Consequently the availability of strontium-90 from soil to plants becomes an important factor in hazard evaluation. We believe information regarding availability, and any change with time thereof, can be obtained by successively cropping soil cultures which have been uniformly contaminated with strontium compounds of varying solubility.