i6o 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



Russell 1 states that single salts of potassium, magnesium, 

 sodium, etc., are toxic to plants, in water culture, while a mixture 

 of salts is not. Breazeale and Le Clerc 2 show that wheat seed- 

 lings grown in culture solutions containing 10 parts per million of 

 potassium chloride or potassium sulphate, cause the solution to 

 become acid. The acidity affects injuriously the development 



go on 



Fig. 38. Wheat seedlings (second crop) grown in, (i) distilled water, (2) 



distilled water and calcium carbonate, (4) potassium sulphate 



and calcium carbonate, compared with (3) those grown 



in potassium sulphate solution. 



of succeeding plants grown in the solution, and a similar effect is 

 shown by solutions of sulphuric acid or hydrochloric acid. 

 Sodium hydroxide, lime, ferric hydrate or carbon black, remove 

 the acidity and render the solution less injurious. 



1 Soil Conditions and Plant Growth, p. 43. 



2 Bulletin No. 149, Bureau of Chemistry. 



