440 VEGETABLE GARDENING 



for the home table, their structure should be modified by 

 the addition of large amounts of vegetable matter. The 

 vine growth is likely to be excessive on stiff soils and the 

 tubers are rough and unsymmetrical. New land is re- 

 garded especially valuable for this crop. Calcareous 

 soils, when properly handled, often produce good results. 

 Some of the driest and most sandy soils give good yields 

 of fine tubers when seasonal conditions are favorable. 

 Sweet potatoes can often be made to pay on lands too 

 poor for cotton or tobacco, although the highest yields 

 cannot be expected in impoverished soils. 



629. Seed. The tubers for the propagation of plants 

 for next year's crop should be selected when the crop is 

 dug. Some growers attend to this matter with the great- 

 est care. Individual hills are studied and the tubers are 

 chosen with reference to productiveness, size, shape and 

 uniformity. With white potatoes, hill selection has 

 been clearly demonstrated to be valuable, and there are 

 reasons for its practice with sweet potatoes, but the ex- 

 perimental evidence in its favor is not very conclusive. 

 The same may be said with reference to the use of 

 tubers of various sizes. The experiment stations have 

 not been able to show that it is profitable to use large 

 tubers for seed, although there is some evidence in their 

 favor. In many regions of prominence the small tubers 

 are chosen because they keep better than large ones 

 in storage, are worth the least on the market, and a 

 bushel will produce a greater number of plants than 

 larger tubers. When several "drawings" are made, from 

 1^2 to 2 bushels of small potatoes are required to grow 

 enough plants for an acre ; 2 to 4 of medium size and 4 to 

 10 of large size to plant the same area. (U. S. D. A. 

 Farmers' Bui. 26, p. 9). The medium size, 2 inches in 

 diameter or less, is preferred by many growers. A 

 bushel will produce from 2,000 to 2,500 plants when two 

 drawings are made. Varieties vary greatly in their 



