juneis, I9IS Antagonism between Anions as Affecting Barley 215 



such conceptions, which we ofifer as a tentative explanation, it seems easy 

 to see why improvement is at first wrought in the clay-adobe soil by the 

 sodium-chlorid and sodium-sulphate treatment and later why a depres- 

 sion is produced by the same salt treatment in the second crop. Actually 

 the toxic effect appears to be there from the beginning but is obUterated 

 by the good effects on the physical condition of the soil wrought by the 

 salt. Given a good physical condition in the soil, however, the toxic 

 effect of the salt becomes easily manifest. 



Another matter of interest arises in connection with the behavior of 

 sodium carbonate. It will be noted in the discussion of the last para- 

 graph that the effects of sodium chlorid and sodium sulphate only are 

 considered and not sodium carbonate. This is done advisedly, since an 

 examination of Table I will show that sodium carbonate acts in a different 

 way from the other salts, especially in the second crop. This, it would 

 appear to us, is to be explained on the basis of the distinctive effects of 

 that salt in a chemical and physiological way. As explained by the 

 senior writer in other publications sodium carbonate is a stimulant to 

 ammonification and a deterrent to nitrification. It is possible, therefore, 

 and this is offered merely as a speculation, that stimulated ammonifica- 

 tion may result in the direct absorption by the barley of ammonia instead 

 of nitrate; and, if ammonia can be readily assimilated by the barley 

 plant, the large amount of ammonia produced by the soils treated with 

 sodium carbonate should cause marked vegetative development owing 

 to better nitrogen feeding; hence, more dry matter. Moreover, other 

 important considerations enter into this problem. Sodium carbonate is 

 readily transformed into other forms when it is mixed with the soil and 

 carbon dioxid (CO2) is given off in accordance with the same principle 

 which Maclntire et al. (9) have shown to apply to magnesium carbonate 

 when it is mixed with the soil. We should thus obtain other compounds 

 of sodium, probably silicates of that element, which would react differ- 

 ently from sodium carbonate. The marked solvent effect on soil min- 

 erals, moreover, which is possessed by this salt would seem to indicate a 

 larger supply of available plant food in the soils treated with this salt and, 

 hence, better plant growth. All of these beneficial effects of sodium 

 carbonate could far outweigh its detrimental effects on the physical con- 

 dition of the soil and yield the results noted. Indeed, in our more recent 

 work we have obtained results that render questionable the great powers 

 attributed to this salt in destroying the physical condition of all soils or of 

 affecting plants deleteriously. 



Pursuant to the last-mentioned idea, it is not out of place here to state 

 in general that the direct toxic effect on plants of the "alkali" salts under 

 consideration has been much exaggerated. The question of alkali toler- 

 ance by plants would appear in the light of our recent experiments to 

 resolve itself really into one of alkali tolerance by soils. It is the effect of 

 salts on the latter that is more likely to result seriously for plants than the 



