21
In controlled experiments, Menzel> has shown that the evailable strontium-90

Se

Menzel, R. Ge, Soil Science 77, 419 (195k).

to available calcium ratio in plants is about half the corresponding soil ratio,

Under uncontrolled field conditions, the relation of plant and soil level will
be influenced by many complicating factors including possible leaf retention
of strontium-90 fallout, variable root depth and soil moisture depth, the sharp
gradient of strontium-90 concentration in the soil surface layer, and the application of fertilizers containing calcium.

These factors undoubtedly account

for considerable scatter in the results.

In the last column of Table 5, the strontium-90 to calcium level in alfalfas are arbitrarily compared to the same ratio in the 0-2" layer of the soils
on which they were grown.

The results appear quite reasonable with the excep-

tion of those for McKee, Van Winkle and Carver farms,
The high concentration for the McKee farm plant material may be explained
by the fact that the sample taken was a mixture of bromegrass and ladino clover
with shallower root depth than that of alfalfas and thus may relate to a higher

soil level.

Furthermore, the growth was short and sparse and was gleaned from

several scattered patches apart from the point of soil sampling.

Thus, differ-

ences in soil calcium or strontium-90 or a higher leaf retention effect may be
involved.

That this sample is not charectcristic of the avcrage McKee farm

vegetation is indicated by the result of 0.51 © 0.03 S.U. for the bone of a

McKee farm stcer killed in September 1955 (sce CL 813-P and compare with
CL 1011 and 1012).

The three 1955 Chicago Milkshed animal bone samples show

the lowest strontium-90 level for the farm with the highest soil calcium level
and the highest bone level for that of the lowest calcium, as would normally

be expected,

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