POTATOES 345 



POTATOES AS A FARM CROP AT THE NORTH 



Up to within comparatively recent years the chief center of pro- 

 duction of the Irish potato in America was in the northern and 

 eastern United States. There the cultivation of the crop took on 

 two characteristic phases the growing of early potatoes and 

 of late, or winter, potatoes. These two crops were founded on 

 varietal differences rather than on different methods of culture. 

 There is sufficient difference in the time required for the growth 

 and maturity of different varieties to enable growers to select those 

 which, if planted early, will produce edible tubers in a compara- 

 tively short time, and others which, even if planted at the same 

 time, will not produce edible tubers until the cool, mild weather of 

 autumn comes on. This accounts for the two crops at the North. 



Kind of soil. A glance at the map, figure 126, shows that the 

 late-potato section of the country is almost completely included 

 within the area covered by the great ice age. In other words, 

 the area in which winter potatoes are most extensively grown falls 

 within the limits of the glacial-drift formation of the United States. 

 There are exceptions to this, particularly in the Pacific coast region, 

 where the upheaval of the great mountain ranges has thrown the 

 isothermal lines far to the south. The great potato fields of 

 Colorado, while high, are considerably south of the territory in 

 which this industry is chiefly found, the altitude compensating for 

 the latitude, as is indicated both by the flora of the region and by 

 the isothermal conditions. In general, it may be said that the soil 

 best suited to the cultivation of the potato is a gravelly or sandy 

 loam, not too light in character, and still not a stiff clay, although 

 potatoes of good quality and a fair yield are produced upon some- 

 what retentive clay soils. 



It is believed that the character of the soil has more influence 

 on the quality of the potato than on the yield. The yield is more 

 largely determined by the kind and amount of fertilizer and seed 

 used, the cultivation given, and the climate than by the character 

 of the soil. The heaviest yields of potatoes are obtained in the 

 higher latitudes where the soil conditions are congenial, that is, 

 where there is a moderately retentive loamy or gravelly soil. The 

 lowest yields are usually obtained in the trucking regions where 



