USE OF RADIOACTIVE SUBSTANCES AS FERTILIZERS. 9 



This was mixed with commercial fertilizers in the following pro- 

 portions: Steamed bone, 20 parts; superphosphate, 15 parts; kainit, 

 10 parts; nitrate of soda, 5 parts; and radioactive manure, 1 part. 

 One plot received an application of this mixture at the rate of 1,020 

 pounds per acre, and an adjoining plot received the same application, 

 but without the radioactive manure. Both plots were planted to 

 turnips, and when the crop was grown it was found that the yield 

 was greatest in the plot to which the complete fertilizer, plus the 

 radioactive manure, had been added. A similar result was obtained 

 with mangels. 



Radioactive material of exactly the same composition as that given 

 by Foulkes was also used by Malpeaux 1 in making pot and field 

 experiments with oats, potatoes, sugar beets, and mangels. The ma- 

 terial was mixed with a complete fertilizer made up of sodium ni- 

 trate, superphosphate, and potassium sulphate to the extent of 5 per 

 cent and applied at the rate of 22 to 44 pounds per acre. In the case 

 of oats, sugar beets, and mangels, an increased yield of about 15 per 

 cent was obtained on an average on the plots to which complete fer- 

 tilizer, plus radioactive material, was added, over that obtained from 

 the plots to which complete fertilizer only was added. In the case 

 of potatoes, it was not observed that the radioactive material had 

 any beneficial effect. 



A very extensive series of experiments was also carried out by 

 Berthault, Bretigniere, and Berthault, 2 using material for which 

 exactly the same analysis was given as for the radioactive manure 

 used by Foulkes and by Malpeaux. Its effect on a large number of 

 crops (cereals, grasses, and roots) was tested by applying the ma- 

 terial alone and when mixed with standard fertilizers. It was found 

 that when the radioactive manure was used alone the positive and 

 negative results were about equal for the total weight of the plants 

 and for stalks and grain, but the negative results were the more 

 numerous for tubers ; with superphosphate the results obtained were 

 generally unfavorable, particularly for the grain, but for tubers they 

 were more often favorable; and with complete fertilizer the favor- 

 able results were the more numerous for all crops. 



It was concluded that while the results obtained were not decisive, 

 they show that radioactive substances were more efficacious in the 

 presence of a complete fertilizer than when used alone, or with phos- 

 phate or nitrogenous manures. 



It is difficult, however, to understand how this conclusion regard- 

 ing radioactive substances follows from the experiments described by 

 the authors, in view of the fact that they acknowledge having had the 

 material which they used tested for radioactivity and that none 

 could be detected. It therefore follows that the results obtained, 



1 Vie Agr. et Rurale, 2, 241 (1913). 2 Ann. ReoTe Nat. Agr. Grignon, 3, 1 (1912). 



