18 



VIII. MANAGEMENT 



A. T he Effect of Liming 



The effect of calcium on strontium uptake has been discussed to some extent in 

 two previous sections. A practical application of this is in the liming of acid soils. 

 The uptake of strontium from different soils increased in proportion to the reciprocal 

 of the exchangeable calcium (24, 66). No relation has been found between the total 

 calcium or calcium carbonate content and strontium uptake (22, 30). Since soils have 

 finite exchange capacities, overliming has little additional effect on strontium uptake. 

 This is demonstrated by the application of lime to neutral or alkaline calcareous soils, 

 which reduces the strontium uptake only slightly (30, 98, 105, 139). A fourfold re- 

 duction of strontium uptake by liming acid soils is generally the most to be expected 

 (109, pp. 18-49). 



The ratio of radioactive strontium to calcium in the plant is as important as 

 the radioactive strontium concentration because deposition of radioactive strontium 

 in animal skeletons depends on the calcium content of the diet (18). Liming tends to 

 decrease this ratio until the exchange capacity of the soil becomes saturated with 

 bases. Then, when the soil is no longer acid, additional lime remains undissolved 

 and thus unavailable to the plant. Therefore, although liming serves a twofold 

 purpose of reducing both the strontium concentration and the strontium-to-calcium 

 ratio, the lowest values for both are usually achieved at a point that coincides with 

 the amount of lime needed for maximum crop yields. 



B. Fertilizers 



In some experiments, fertilizer has increased the uptake of fission products, 

 but in others no increase occurred (14, 47, 117, 120). Fertilizers and manures may 

 affect the availability of the fission products, as discussed in previous sections, 

 but it is possible that better plant growth will obscure any other effect. 



C. Cultivation 



Cultivation tends to increase strontium uptake by some crops (14), possibly by 

 providing more root contact. Greater uptake of calcium results from a completely 

 mixed calcium application than from a banded application (12). Increased uptake of 

 strontium in the second year of a field experiment has been attributed to a more 

 uniform distribution of strontium (14). In the case of shallow -rooted grasses, as dis- 

 cussed under species differences, it appears that plowing reduces the strontium- 90 

 to calcium ratio of the new plamting (72). 



