292 SWEET POTATOES 



on heavy soils, the lighter type of soil is considered decidedly better. 

 Good drainage is especially important for sweet potatoes, and this is 

 one reason why in many places they are frequently grown on high 

 ridges. Sweet potatoes on wet land are usually coarse and poor 

 in quality. 



Manure and Fertilizers for Sweet Potatoes. If barnyard 

 manure is used, it should be well rotted and usually applied to the 

 previous crop, although in light, sandy soils it is very commonly 

 applied directly to the sweet potato crop. Barnyard manure is very 

 beneficial to exhausted soils, but with fairly fertile soil it is probable 

 that better results can be secured by the use of commercial fertilizers. 

 Where sweet potatoes are grown as a regular crop, it is considered 

 very beneficial to turn under a green manure crop about a month 

 before planting the sweet potatoes. Crimson clover is generally 

 agreed to be about the best crop for this purpose. 



Sweet potatoes respond exceptionally well to commercial fer- 

 tilizers, and they are generally used in growing the crop on sandy 

 land. It is generally believed that on sandy lands potash is of the 

 greatest importance, and phosphate next, in making the fertilizer? 

 for sweet potatoes. Some nitrogen should be supplied, but not an 

 excessive amount, as it would stimulate too large a growth of vines. 

 In general, a fertilizer containing about four per cent of nitrogen, 

 six to eight per cent of phosphoric acid, and eight to ten per cent of 

 potash is recommended. On clayey soils, however, the per cent of 

 potash can be somewhat reduced to advantage. 



Applying Fertilizers. Ordinarily about 300 to 400 pounds of 

 fertilizers are applied per acre, but in the trucking regions along the 

 Atlantic Coast 1000 or 1200 pounds are frequently applied. When 

 300 or 400 pounds are used, it is generally applied under the sweet 

 potato row a week or two before planting, but the larger amount is 

 generally applied broadcast. 



Preparation of Land. The sweet potato crop should be grown 

 in a regular rotation, coming on the same land not oftener than once 

 in three or four years. It is best to precede the sweet potatoes with 

 a cultivated crop, such as corn or cotton, in which a cover crop, such 

 as crimson clover or hairy vetch, has been fall-sown. The plowing 

 under of such a cover crop seems to be an ideal preparation for sweet 

 potatoes. 



