100 The Potato 



(5) Potato-growing by the so-called dry-farming methods, 

 and local conditions such as the delta section of California, 

 are as yet less important types. 



SOILS 



The choice of the soil on which to grow the potato is 

 peculiarly difficult because of the fact that those which 

 best meet the needs of the plant in one respect may be 

 unfitted for it in others. Sandy soils permit free develop- 

 ment of the root system, are well drained and are capable 

 'of early tillage in spring. Although usually poor soils 

 unless fertilizer is applied, the growth of the crop is rapid ; 

 and for these reasons most of the early truck crop of the 

 South is grown on sandy soils, as earliness secures the 

 highest prices. The great problem of potato-growing on 

 sandy soils is that of sufficient water supply at the time 

 the tubers are forming. This tendency to drought and 

 heat injury of the crop has operated to lessen the use of 

 sandy soils in the northern states for the late main crop 

 in favor of soils cooler and more retentive of moisture. 

 A large proportion of organic matter is of great value to 

 sandy soils in increasing available fertility and the ability 

 to hold moisture. The organic matter in sandy soils is 

 easily exhausted by tillage, and constant effort is needed 

 to keep it up to a high standard. 



The larger part of the potato crop of the United States 

 is grown on soils ranging in texture from sandy or gravelly 

 loam to clay loam. Such soils are capable of holding 

 enough moisture to supply the growing plant continu- 

 ously, are cooler than the sands, and are usually of fair 

 fertility if not too deficient in organic matter. While the 

 extension of tlie roots and the formation of the tubers 



