SOIL CONDITIONS AFFECTING PLANT GROWTH 71 



replace potassium as a plant nutrient ; it thus delays the 

 setting in of potash starvation, but will not keep it off alto- 

 gether. Hellriegel (130^) found that sodium salts always 

 gave increases in crop even when potassium salts were present 

 in quantity. 



Table XXIII. — Effect of Sodium Salts with Small and with Large 

 Amounts of Potassium Salts on the Growth of Barley. 

 Hellriegel (i3o<^. 



Breazeale (5l<^) has more recently obtained similar results 

 in water cultures. It is well ascertained in farming practice 

 that sodium salts can be used with great effect as manures 

 wherever there is any deficiency of potash in the soil.^ 



J. A. Voelcker (290) has made the interesting observation 

 that sodium hydrate and sodium carbonate, unlike most other 

 salts, cause an increase in the percentage of nitrogen in the 

 wheat grain, besides increasing the yield of crop. The sulphate 

 and the chloride increased the crop, but beyond a relatively 

 low concentration limit further increases in amount of sodium 

 chloride proved toxic. 



Lithium salts, on the other hand, have a toxic action on 

 plants. Gaunersdorper's older experiments ^ have been con- 

 firmed by J. A. Voelcker (290, 191 2), who found that amounts 

 of the chloride, sulphate, or nitrate, corresponding to -003 

 per cent, of the metal were distinctly injurious to wheat ; 



^For fuller details see Kruger, Zeitschr. Ver. Deut. Zuckerindus., 1914, 694- 

 702; B. Schulze, Beitrag zur Frage der Diingung mit Natronsalzen (Landw- 

 Versuchs-Stat., 1913,79-80,431, and 1915, 86, 323-330); E. J. Russell, yowrw. 

 Bd. Agric, 19 15, 22, 393-406. 



'^ Landw. Versuchs-Stat., 1887, 34» 171-206. 



