J. F. LOUTIT 



A second experiment has been concerned with, as it were, the comparative 

 physiology of different species of plants. Rye-grass, clover and lucerne have 

 been grown in deep boxes. In some boxes a layer of ^^Sr has been placed one 

 inch below the surface. In other boxes the ^^Sr has been placed at the 

 six-inch or twelve-inch level. These boxes have been sampled on three 

 occasions. The young growing plants, of course, all take up *^Sr from the 

 one-inch layer but on the third occasion when the plants were all well 

 established, rye-grass still took up much more ^^Sr from the one-inch layer 

 than from the other two. In the case of clover the uptake was much the same 

 from all three layers, but by lucerne, known to be a deep feeder, the uptake 

 from the twelve-inch layer was greater than from the other two. This shows 

 us that the pasture grasses, like rye-grass, are especially likely to take up 

 fall-out strontium in unploughed permanent pasture, because the ^"^Sr 

 moves extremely slowly through the soil and remains concentrated in the 

 top inch or two. Ploughing of pastures would help to redistribute the 

 strontium through the soil profile and to dilute it. The pasture could then 

 be reconstituted by reseeding. The practice of turning over leys every three 

 to five years is already recommended as good agricultural practice. 



However, we have seen that not all contamination comes from the soil 

 through the roots. Middleton^^ has already published some of his observa- 

 tions on the accumulation of ^^Sr and ^^'^Cs in the edible parts of agricultural 

 crops. Boxes containing the various species at different stages of growth have 

 been contaminated with a fine spray of soluble salts of these nucleides. This 

 necessitates a specially designed spraying chamber. After spraying, the crops 

 were dried off and later exposed to wind and rain. Much of the radio- 

 activity was lost by being washed off with rain or in other ways such as the 

 decay of the older leaves. Some of the ^^Sr was absorbed by the leaves and 

 remained in situ. Little, if any, entered the vessels so that there was little 

 translocation to developing edible parts of the plants. ^^'^Cs was also 

 absorbed through the leaves but this did enter the circulation and some 

 appeared subsequently in edible parts of the plant — young leaves and fruit, 

 roots and tubers. 



Laboratory experiments such as these are being carried out and have 

 been reported in other parts of the world. What is perhaps unique are 

 some of the experiments planned and carried out in the field in Great Britain. 



Milbourn, Ellis and RusselP* have used plots of land roughly one acre 

 in area in various parts of the country, each with a different soil type. The 

 areas have been sprayed with ^^Sr — special precautions being taken to 

 prevent contamination of the staff undertaking the spraying operation. The 

 sprayed area has then been cultivated by one or other of three different 

 methods, shallow scuffling with a rotary cultivator, ploughing to the con- 

 ventional depth of six or seven inches, or deep ploughing to twelve inches. 

 In some cases a cultivated and sown area has also been sprayed with ^^Sr or 

 an established pasture has been contaminated. The contaminated and 

 subsequently cultivated plots were sown with crops — rye-grass, cereals and 

 root or fodder crops. In the case of rye-grass the uptake was by far the 

 greatest when pre-sown areas were contaminated just before the seed 

 germinated. Next in general order were those areas first contaminated and 

 then cultivated with rotary cultivators. As might be expected the uptake 



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