THE LIME-MAGNESIA RATIO 93 



From another standpoint Robert Stewart- discusses the prob- 

 lem of Loew's lime-magnesia ratio. He gives consideration to 

 analyses of the soils of the Utah Agricultural Experiment Station 

 tract, in certain of which the content of calcium carbonate amounts 

 to 30 to 41% whereas the content of magnesium carbonate va- 

 ries from 11 to 20% down to a depth of eight feet. These soils 

 had been cropped at the time Stewart wrote, for forty years 

 without manuring. The author claims that because of the fact 

 that no toxic effect has been visible in these lands so far as crops 

 are concerned, that the lime-magnesia ratio, which in this case 

 is about 3:1, is the factor which prevents such toxic effects. 

 He believes that the calcium and magnesium are found there in 

 the double salt form CaMg(C03)2 and that therefore magnesium 

 carbonate alone is present in small quantity, and can not be 

 harmful. He refers to the possibility of the different effects 

 which might be brought about by either calcium carbonate or 

 magnesium carbonate alone, as against the effect of the double 

 salt just referred to. For that reason it seems wise to Stewart 

 that magnesian limestone be employed for correcting soil acidity. 



At about the same time that Stewart's paper appeared, there 

 was published the report of J. A. Voelcker-^ of the Woburn Agri- 

 cultural Experiment Station in England. In pot experiments 

 covering a long period, it was found that the addition of magne- 

 sia was beneficial to the growth of wheat, provided it never ex- 

 ceeded the ratio of 1 : 1 to the Hme content. When added be- 

 yond that, the magnesia is toxic. Grain soils containing an ex- 

 cess of magnesia, according to Voelcker, are benefited by a hme 

 application, but lime, on the other hand, in excess, is not toxic 

 like magnesia. Both lime and magnesia were found to affect 

 the general growth of the plant and the root development, and 

 they are said to induce a greener color to the flag and a higher 

 nitrogen content in the grain. 



In concluding these investigations favorable to the hypothesis 

 of the lime-magnesia ratio, and before proceeding to a review of 



" Jour, of Ind. Eng. Chem., vol. 3, p. 376. Cited from E. S. R., vol. 26, p. 723, 

 1912. 



-5 Jour. Roy. Soc. Eng., vol. 73, entire Ser., p. 325, 1912. 



