New York Agricultural Experiment Station. 247 



conclusions. 



The conclusion that potash stands in a different and mucb 

 more important relation to the physiological needs of plants than- 

 d'oes soda cannot be evaded, and there is no reason for modifying^ 

 the deductions drawn from the data of the early investigators. 



A discussion of the substitution of soda for potash in plant 

 growth may be answered with reference to (1) substitution in 

 quantity and (2) substitution in function. 



Suhstitutimi of soda for potash, in quantity. — There is no ques- 

 tion but that in these experiments the dry matter of those plants- 

 having access to a very limited supply of potash and a free sup- 

 ply of soda contained a much larger proportion of soda than 

 where potash was present in abundance. The percentages of 

 soda where the potash was deficient were from one-half to five 

 times greater than where the salts of both alkalies were liberally 

 supplied. In this sense potash was substituted for soda. Limit- 

 ing the supply of soda did not effect an equal increase of potash,, 

 althongh tliere appeared to be a tendency in some instances to- 

 substitute potash for soda. 



Siibstitution of soda for potash, in function. — The most important- 

 question in this connection is, Did the increase m soda, taken 

 up by the plants make good the deficiency of potash by promot- 

 ing the growth of the plant to the same extent as the potash?' 

 In other words, Can soda be substituted for potash in function? 

 This question must be answered in the negative so far as these 

 experiments throw any light upon it, and the results here pre- 

 sented stand in entire accord with the great mass of testimony- 

 furnished by previous investigations. 



In these experiments the lack of potash was fatal to the vigor- 

 ous development of the plants. This is especially shown in the 

 results of 1899-1900 where the supply of potash was limited to a 

 verj small quantity. While the plant appropriated increased 

 junounts of soda when the potash was deficient, this seemed to be- 

 of no avail in making good the lack of potash. On the other 

 hand a lack of soda appeared to be no disadvantage whatever^ 

 when potash was present in a sufficient amount. 



