244 Fertilizers 



richer in the plant-food elements, though the proportion 

 of potash, as in the formulas already indicated, should 

 be relatively large. The nitrogen may be reduced, and 

 the form of nitrogen may be derived largely from quickly 

 available organic sources. Good formulas for late po- 

 tatoes may consist of 



Nitrogen 3% 



Phosphoric acid 6% 



Potash 8% 



and the application may be from 800 to 1200 pounds to 

 the acre. 



Where potatoes are grown in rotations with the cereal 

 crops mentioned in Chapter XII, the unused residue from 

 the rather heavy application of fertilizers to the potato 

 crop is depended upon to aid very materially the growth of 

 these, thus reducing the outlay for fertilizer for crops of 

 a low commercial value. This practice is advantageous, 

 though the prime object should be to feed the crop rather 

 than the soil that is, apply the fertilizer with the idea of 

 securing a profit from it in the potato crop, rather than a 

 possible profit in subsequent crops. 



SWEET POTATOES 



In the growing of sweet potatoes, the quality of the prod- 

 uct is more important than in the case of the white potato. 

 The northern markets distinctly recognize quality in this 

 crop, and it is measured by size, shape and results in cook- 

 ing. The potato that brings the best price in the different 

 markets is small, about the size of a white potato; in 

 shape round, rather than oblong, and is dry and mealy 

 when cooked. This characteristic of the crop is influenced 



