190 



The area devoted to potatoes during the last decade was two and 

 a half million acres annually. Potatoes do best on a moderately 

 moist and deep soil and in a climate relatively cool. 



Since the period of growth is short, varying from three to five 

 months, they should be planted in soil which has an abundance of 

 readily available plant food. Notice in Fig. 101 that most of the 

 underground stems which have produced potatoes leave the main 

 stem about four inches below the surface and but a short distance 

 above the seed-piece. This suggests that the seed should be planted 

 about four inches deep. To produce three hundred bushels of pota- 

 toes requires the exhalation of over three hundred tons of water ; 

 therefore water or moisture is of quite as much importance in 

 securing large yields as plant food. 



It is best to prepare the land deeply, to plant deep, and then to 

 practice nearly or quite level culture. The practice of hilling up 

 potatoes, so common in most parts of the country, is to be discour- 

 aged, because it is wasteful of moisture and the tubers do not grow 

 in the coolest part of the soil. For very early potatoes, hilling-up 

 may be allowable. Till the soil very often to save the moisture. 

 For the philosophy of this see Leaflet 'No. 15. 



x^ot infrequently the potato is seriously injured by blights which 



attack the leaves. The early blight, which usually appears in June, 



may destroy some of the foliage, thereby checking growth. The 



late blight, which also attacks the foliage, is far more serious. It 



differs little in outward appearance from the early blight. In rare 



cases the vines are so seriously injured that no potatoes are formed. 



The potato rot or blight did great damage to the potato in many 



localities in the United States in 1845. In 181:6 the blight appeared 



in Ireland and virtually destroyed the entire crop. Previous to this 



date the potato had become the chief food supply of the peasantry. 



The cultivation of the oat as a food crop had been universal previous 



to the introduction of the potato, but oats furnished so little food 



on a given area as compared to the potato that its cultivation at the 



time the blight appeared had been very largely abandoned. The 



loss of the potato crop produced widespread famine. The most 



conservative estimate of the numbers who perished for want of food 



290 



