396 soils: fiwfebties and management 



Although in general the results as to the resistance to 

 alkali of the various crops are so conflicting, the Bureau 

 of Soils/ in its alkali mapping, has been able to make a 

 rough classification as follows : — 



Percfntage of Total 



Pekcentagc or 



n'pri'pct 



Salts 



Bl^ck Alkali 





to 0.20 



Less than 0.05 



All crops grow 



0.20 to 0.40 



0.05 to 0.10 



All but most sensitive 



0.40 to 0.60 



0,10 to 0.20 



Old alfalfa, sugar beet, 

 barley, and sorghum 



0.60 to 1.00 



0.20 to 0.30 



Only most resistant plants 



1.00 to 3.00 



0.30 and above 



No plants 



307. Other conditions that influence the action of 

 alkali. — The higher the water content of the soil, the 

 less is the injury to plants from alkah; but should 

 the same soil become dry, the previous large quantity of 

 water would, by bringing into solution a larger amount 

 of alkali, render the solution stronger than it would 

 otherwise have been, and thus cause greater injury (see 

 Fig. 57). 



The distribution of the alkali at different depths may 

 have an important bearing on its effect on plants. 

 Young plants and shallow-rooted crops may be entirely 

 destroyed by the concentration of alkali at the surface, 

 while the same quantity evenly distributed through the 

 soil, or carried by moisture to a lower depth, would have 

 caused no injury. A loam soil, by reason of its greater 

 water-holding capacity and adsorptive power, will carry 

 more alkali without injury to plants than will a sandy 



1 Porsey, C. W. Alkali Boils of the United States. 

 D. A., Bur. Soils, Bui. 35, pp. 23-25. 1906. 



U. S. 



