POTATOES 171 



of machines drawn by horses (Fig. 87). One of the smaller 

 forms is shown in Fig. 87a. Larger machines elevate the 

 tubers, shake off the dirt, and drop them on the ground. 

 They are drawn by three or four horses. Small garden 

 patches are dug by hand tools. 



Weights and Yields. The legal weight of' a bushel of 

 potatoes is sixty pounds, except in Pennsylvania and Vir- 

 ginia, where the weight is fifty-six pounds. The yields are 

 often two hundred and fifty bushels or more per acre, but 



Fio. 87o. An inexpensive potato digger to be drawn by one or two horses. 



(Plant Industry.) 



the average is about one hundred bushels per acre. The 

 value of the crop in the United States each year is about 

 $100,000,000. 



SWEET POTATOES. 



The sweet potato is grown to a limited extent in nearly all 

 the northern States, but the best qualities and largest 

 quantities are produced in the southern States. The plant 

 is of tropical origin. 



. Soil. Sweet potatoes thrive best on a rather sandy 

 loam which does not contain too much of organic matter. 

 Soils that are too poor for the production of most other 

 farm crops may suit sweet potatoes very well. 



Starting the Plants. New plants are started in early 



