Climate, Soils and Rotation 97 



the crop safely through heat and drought which would 

 not only badly reduce the yield but also spoil the crop 

 for use as seed. Practically the whole yield is produced 

 after this time. 



Type, variety and strain 



In this chapter, reference to the seed used is made to 

 show that the variation between different types, varieties 

 and strains allows the grower considerable latitude in 

 adjusting the potato crop to different conditions. The 

 use of quickly maturing types in the South and of heat- 

 resistant types in all but the most northern sections are 

 examples of these adaptations. Much effort has been 

 expended in the effort to find new varieties possessing the 

 quality of resistance to some of the more serious potato 

 diseases, but with little success as yet. 



Diseases 



Several of the most important potato diseases affect 

 cultural methods. Examples of such are the use of long 

 rotation to eliminate common scab, rhizoctoniose, the 

 nematode eelworm and the fusarium wilt, from affected 

 soils. Early spring planting to insure maturity before pos- 

 sible attacks of late-blight is employed in some sections. 



GENERAL TYPES OF POTATO-GROWING IN THE UNITED 



STATES 



Conditions of climate, soil, seed and markets vary so 

 much that every grower has his problem to select the 

 methods which will give him the most profitable results. 

 The climate is something the grower cannot change. 



