330 



NATURE AND PROPERTIES OF SOILS 



Table LXXV 



COMPARISON OF ALKALI EXPRESSED IN PERCENTAGE OF THE DIF- 

 FERENT SALTS PRESENT. 



Carbonates of the alkalies, particularly sodium carbonate, 

 dissolve organic matter from the soil, thus giving a dark color 

 to the solution and to the incrustation. For this reason, alkali 

 containing large quantities of these salts is called black alkali. 

 Black or brown alkali may also be produced by calcium chlo- 

 ride or by an excess of sodium nitrate. 



Black alkali is much more destructive to vegetation than is 

 the white. A quantity of the latter which would not seriously 



a Headden, W. P., The Fixation of Nitrogen; Colo. Agr. Exp. Sta., 

 Bui. 155, p. 10, 1910. 



2 Hilgard, E. W., Soils, p. 442, New York, 1906. 



•Dorsey, C. W., Alkali Soils of the United States; U. S. Dept. Agr., 

 Bur. Soils, Bui. 35, 1906. 



