SOIL ACIDITY 347 



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

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

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

 unproductive soil. In 1918, Hartwell and Pember^ 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 ^ indi- 

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



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.^ 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^ with 



^ Abbott, J. B., Conner, S. D., and Smalley^ H. E., Soil Acidity, NitH- 

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

 Sta., Bui. 170, 1913. 



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

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

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



^Mirasol, J. J., Aluminum as a Factor i% Soil Acidity; Soil Sci._, 

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



^ See also, Kratzman, E., Zur Physiologischen Wirlcung der Aluminium 

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



Rupreeht, 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. 



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

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

 124, 1921. 



'^Conner, S. B,, 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 

 Sei., 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 Beid, F. R., The Action of Manganese Under Acid 

 and Neutral Soil Conditions; XI. S. Bept Agr., BuL 441, 1916. 



