DAIRY AND SEED IMPROVEMENT MEETINGS. 399 



this terrible European war now raging, which prevents the im- 

 portation from Europe of the German potash salts. There is 

 probably from a quarter to a third as much potash in the United 

 States as would normally be used in the 191 5 fertilizers, and 

 hence the question which confronts the fertilizer manufacturer 

 and the user of fertilizers is, how to use this limited supply to 

 the best advantage. 



An acre of soil to the depth of one foot in the potato grow- 

 ing districts of Elaine carries from four to six tons of potash 

 salts soluble in strong acid. Gradually by soil action this potash 

 is rendered available to growing plants. With the three and four 

 year rotation fairly common in Maine potato districts the 

 crops remove from 225 to 300 pounds of potash per acre. 

 Three hundred bushels (no barrels) of potatoes will remove 

 about 90 pounds of potash, 50 bushels of oats, about 45 pounds 

 of potash and two crops of two tons of clover and timothy, 

 about 180 pounds. Most of the fertilizer used in these rotations 

 in the potato growing sections is applied for the potato crop. 

 The application will carry from 125 to occasionally 200 pounds 

 of potash per acre. Hence it is evident that in this rotation 

 there is a constant drawing although small upon the reserve 

 stock of potash. In field experiments potash has rarely been a 

 determining element in the yield of the potato crop. 



NITRATE OF SODA AND THE POTASH OF THE SOIL. 



A field experiment which has been conducted for 20 years 

 at the Agricultural Experiment Station of the Rhode Island State 

 College is probably the most important source of information 

 in this country as to the extent to which soda can replace potash 

 in manures. 



The following results selected by Director Hartwell of the 

 Rhode Island Station from those secured in 1914 serve to indi- 

 cate the value of soda. Different crops were grown upon 

 uniform plots. All were supplied with the needed nitrogen and 

 phosphorus. The potash and soda treatments and the results 

 obtained were as follows : 



Fifteen pounds potash per acre, without soda, gave yields of 

 252 pounds of carrots, 153 pounds of potatoes, and 21 pounds ot 

 onions; 15 pounds of potash per acre, with soda, gave 306 



