10 BULLETIN 149, IT. S. DEPARTMENT OP AGBICTTLTUBE. 



whether of a favorable or unfavorable nature, could not have been 

 due to the radioactivity of the material, but to some other influence. 



As shown in the table, the acidity of the material was equivalent 

 to 65 grams of sulphuric acid per kilogram, while the " soluble 

 phosphoric acid " amounted to 1.37 per cent, and the " soluble salts, 

 soluble free acids " amounted to 3.32 per cent. All these constituents 

 when exceeding a certain minimum concentration have a marked 

 effect on plant growth. Notwithstanding this, however, apparently 

 no account was taken of the presence of these constituents in any 

 of the foregoing experiments, but rather all effects observed, whether 

 of a stimulating or retarding nature, were attributed to the exceed- 

 ingly weak radioactivity of the material, which was claimed to be 

 equal to 0.03 of the activity of uranium, but which at least in the 

 case of the material used by Berthault, Bretigniere, and Berthault, 

 was too small to be detected. 



If it is assumed that the material used in these investigations has 

 the radioactivity which was claimed for it, and that this was due 

 to radium and its products, then it can be calculated that in an 

 application of 25 pounds of the material per acre the amount of 

 radium thus applied to an acre would be less than one one-hundredth 

 of the radium already present on an average in an acre-foot of soil. 

 This amount is so small that when uniformly distributed through 

 the first 6 inches of the soil there would be radiated per second from 

 the material added only about 2 alpha particles — that is, 2 atoms — 

 from each pound of soil. Furthermore, of the particles so radiated, 

 only a very small fraction would be able to escape from the particles 

 of material in which they originate. The number of beta particles 

 radiated would be still less than the alpha particles. 



The radioactive material (B), of which an analysis is given in the 

 table and which was kindly supplied by a firm in this country, has 

 an activity of 0.037 that of uranium, and is therefore slightly more 

 active than the material referred to above. An application of from 

 20 to 25 pounds per acre was recommended, mixed with some stand- 

 ard fertilizer, but even in the case where the largest application is 

 used the quantity of radium so applied per acre is only one-fiftieth 

 of the radium already present in an acre-foot of soil. In defense of 

 the use of such a minute quantity of any substance it has been 

 explained that " this material is not a fertilizer, but that it gives to 

 the plant additional power to consume the plant food that is already 

 in the ground or that is put there by artificial means in the form of 

 any brand of fertilizer." The use of the word fertilizer in this state- 

 ment is no doubt intended to mean a plant food. As already pointed 

 out, however, a material does not necessarily have to act as a plant 

 food to be properly called a fertilizer, for this term is also used with 



