2IO 



Journal of Agricultural Research 



Vol. IV. No. 3 



as compared with the larger amounts in the first crop. We are unable 

 to explain satisfactorily why o.i per cent of calcium sulphate should in 

 the first crop render 0.4 per cent of sodium sulphate much more toxic 

 than it is alone, and in the second crop virtually inhibit its toxicity. 

 This can not be accidental, since the same result is obtained in another 

 set of duplicate pots differing from those just described only in contain- 

 ing 0.15 per cent of calcium sulphate instead of o.i per cent. Similar 

 results have been obtained by the senior writer and Mr. P. S. Burgess in 

 other investigations (6), but they remain as difficult as ever to explain. 

 This case is particularly troublesome, since the same concentration of 

 salts in the same pot gives practically no crop the first season and a very 

 good crop the second season. In the first case the salts show increased 

 toxicity when calcium sulphate is added to sodium sulphate, whereas a 

 few months later the maximum of antagonism is noted with the same 

 salt mixture in the same soil and pot. 



Table V. — Results of experiments on antagonism between calcium sulphate and sodium 



sulphate 



Whatever the cause of this puzzUng fact may be, the results given in 

 Table V leave no room for doubt as to the power of gypsum to antagonize 

 the toxic effects of Glauber salt (sodium sulphate) in a clay-adobe soil, 

 barley being the plant grown. It must also be noted in this connection 



