2i6 Journal of Agricultural Research voi. iv.No.3 



interference of salts directly with the normal functioning of plants. It 

 may further be added that our experiments convince us also that even the 

 effects of salts on soils are of an indirect nature, and, with the exception of 

 cases of soils containing 0.75 per cent of total salts or more, they do not 

 offer very serious practical problems in reclamation. This last remark 

 is offered tentatively only as a hope for the practice of alkali-land recla- 

 mation, but at present seems well supported in fact. 



The curious behavior of gypsum in the first crop. Table V, may be 

 explained from the theoretical standpoint as a result of the fixation of 

 bases, which in turn would change the nature of the soil solution. For 

 example, a relatively small quantity of gypsum, which relatively is a 

 slightly soluble salt, would set free by exchange of bases a certain amount 

 of magnesium in the soil solution. Magnesium, as has been shown by 

 several investigators, is detrimental in some concentrations to plant 

 growth. This might therefore point to a direct toxic effect of magnesium 

 resulting from an application of calcium sulphate. When, however, 

 much more of the latter salt is added to the soil, an excess of calcium is 

 introduced which neutralizes the toxic effects of the magnesium as well 

 as of the sodium sulphate present, and the growth of barley is very much 

 improved. This is offered merely as a speculation of interest and perhaps 

 of significance in connection with the phenomenon noted in the series 

 given in Table V. We recognize in some ways the inadequacy of the 

 foregoing explanation and are not unaware of the flaws in the theory, 

 but we feel that it may lead finally to an explanation of the facts noted. 



In concluding the discussion, we desire to state that many other con- 

 siderations of a theoretical nature enter into the subject of antagonism 

 between anions in soils. The latter are such complicated media, however, 

 and involve so many changes of an intensely complicated nature, that it 

 would be impossible to discuss all these questions here. 



SUMMARY 



Results are given above which establish for the first time, so far as we 

 are aware, the existence of antagonism between anions in a clay-adobe 

 soil for barley as follows : 



(i) Antagonism is shown between sodium chlorid and sodium sulphate 

 and between sodium chlorid and sodium carbonate in the second crop. 

 None is shown in the first crop. 



(2) Slight antagonism is shown between sodium carbonate and sodium 

 sulphate in the first crop. It is questionable whether any exists at all in 

 the second crop. 



In subsidiary experiments the following points are established in 

 addition to those named above. 



(i) Marked antagonism exists in both the first and second crop between 

 sodium sulphate and calcium sulphate in soil cultures. This has not been 

 considered possible hitherto by Hilgard. 



