SOIL ACIDITY 347 



presence of active aluminum in so-called acid soils has been 

 known for some time. Abbott, Conner, and Smalley 1 showed 

 in 1913 that aluminum salts were the toxic agents in a certain 

 unproductive soil. In 1918, Hartwell and Pember 2 proved 

 quite definitely that, for certain soils and for certain crops, 

 the aluminum ion was the injurious factor rather than the 

 hydrogen ion that accompanied it. The work of Mirasol 3 indi- 

 cates that active aluminum is usually present in acid soils. 4 



Although soluble iron is seldom present to an excess, its 

 ferrous salts are known to be toxic to a greater extent than 

 acids of the same concentration. 5 While soluble iron may ac- 

 company active aluminum, it is questionable whether it ac- 

 tually figures in acidity effects. The toxic influence of man- 

 ganese is more probable, since it is more soluble in an acid than 

 a neutral soil. While it is extremely toxic to plants above 

 a certain concentration the recent work of Funchess 6 with 



1 Abbott, J. B., Conner, S. D., and Smalley, H. E., Soil Acidity, Nitri- 

 fication and the Toxicity of Soluble Salts of Aluminum; Ind. Agr. Exp. 

 Sta., Bui. 170, 1913. 



2 Hartwell, B. L., and Pember, F. R., The Presence of Aluminum as a 

 Beason for the Difference in the Effect of So-called Acid Soil on Barley 

 and Bye; Soil Sci., Vol. VI, No. 4, pp. 259-277, 1918. 



8 Mirasol, J. J., Aluminum as a Factor in Soil Acidity; Soil Sci., 

 Vol. X, No. 3, pp. 153-193, 1920. 



4 See also, Kratzman, E., Zur Physiologischen Wirkung der Aluminium 

 Sals auf die Pflanze; Chem. Ztg., Jahrgang 38, S. 1040, 1914. 



Ruprecht, R. W., Toxic Effect of Iron and Aluminum Salts on Clover 

 Seedlings; Mass. Agr. Exp. Sta., Bui. 161, 1915. 



Miyake, K., The Toxic Action of Soluble Aluminum Salts upon the 

 Growth of the Bice Plant; Jour. Biol. Chem., Vol. 25, No. 1, pp. 

 23-28, 1916. M 



Conner, S. D., Liming in Its Belation to Injurious Inorganic Com- 

 pounds in the Soil; Jour. Amer. Soc. Agron., Vol. 13, No. 3, pp. 113- 

 124, 1921. 



6 Conner, S. D., Liming in Its Belation to Injurious Inorganic Com- 

 pounds in the Soil; Jour. Amer. Soc. Agron., Vol. 13, No. 3, p. 114, 

 1921. 



•Funchess, M. J., Acid Soils and the Toxicity of Manganese; Soil 

 Sci., Vol. VIII, No. 1, p. 69, 1919. 



See also, Kelly, W. P., The Influence of Manganese on the Growth 

 of Pineapples; Haw. Agr. Exp. Sta., Bui. 23, 1909. 



Skinner, J. J., and Reid, F. R., The Action of Manganese Under Acid 

 and Neutral Soil Conditions; U. S. Dept. Agr., Bui. 441, 1916. 



