INFLUENCE OF SOIL ALKALI ON BACTERIA 197 



who has done much work in this field considers that the value 

 of calcium lies in its effect at the surface between the absorbing 

 membrane and the external solution and is not due to chemical 

 action inside the cell. He, therefore, explains antagonism by 

 assuming that antagonistic substances prevent each other from 

 entering the cell. For, according to Loeb, if the wrong salts 

 reach the inside of the cell they replace the salts in the protein 

 and the cell dies. 



Out of this work has grown the idea of physiologically bal- 

 anced solutions, or as Osterhout put it, "Normal life is possible 

 only when necessary salts combine with the colloids of living 

 substance in a definite ratio." 



How to Overcome Poisonous Action.— The methods which 

 have been used for eradicating the evils of alkali salts on plant 

 and bacteria are of two classes. The first attempts to inhibit the 

 toxic effects of the salts without removing them from the soil, 

 and the second attempts to overcome the bad effect by the total 

 removal of the salts from the affected soil. 



Neutralizing Salt. — Where the injurious constituent is sodium 

 carbonate and it is not present in too great a concentration it 

 may be combatted by the use of gypsum. The gypsum changes 

 the black alkali into the less toxic sodium sulfate. In addition to 

 changing the salt into a less poisonous substance, this treatment 

 greatly improves the tilth of the soil. Moreover, a preliminary 

 treatment such as this is often necessary before black alkali can 

 be leached from the soil. 



Lipman has shown that the addition of large quantities, thirty 

 to forty tons, of barnyard manure to a soil in which the concen- 

 tration of alkali is not too high will often render the soil produc- 

 tive. This, he considers, to be due to the rapid decay of the organic 

 substance with the formation of large quantities of colloidal mate- 

 rial. This would greatly increase the actual surface on which 

 the salts could be held away from the plants and bacteria. This 

 being the case, as the manure decays the injurious action of the 

 salt reappears. 



Great hopes have been held out by some workers that the in- 



