444 VEGETABLE GARDENING 



in the frame should never fall below 60, and higher 

 temperatures are preferred for some time after the 

 tubers have been bedded. Watering and ventilation 

 must be attended as changing weather conditions de- 

 mand. Flue or steam-heated frames require more fre- 

 quent and abundant watering than manure-heated and 

 nonheated beds. Strong, healthy plants are essential to 

 large yields, but good plants cannot be grown without 

 close, daily attention. 



In the extreme South the tubers are sometimes cut 

 into pieces and planted like white potatoes, and again 

 the small tubers are occasionally planted whole and cut- 

 tings made to extend the plantation. Vine cuttings are 

 commonly used in the most favorable regions. They are 

 usually ID or 12 inches long, and are made after the 

 plants begin to vine. When planted, they are placed 

 horizontally or obliquely with only I or 2 inches of the 

 tip projecting above ground. 



631. Soil preparation. — Weeds must be guarded 

 against by clean cultivation, in making preparations for 

 a crop of sweet potatoes. Rotation is important. A 

 thoroughly cultivated crop, followed by crimson clover, 

 puts the soil in excellent condition for planting sweet 

 potatoes. In sections where climatic conditions permit, 

 it is customary to grow an early crop of peas, beans, cab- 

 bage or other vegetables before planting sweet pota- 

 toes. While a comparatively dry soil is essential to this 

 crop, the supply of moisture must be ample at trans- 

 planting, a fact which must always be kept in mind in 

 all preparatory tillage operations. 



632. Fertilizing. — A yield of 200 bushels an acre will 

 require, for the tubers alone, 30 pounds of nitrogen, 10 

 pounds of phosphoric acid and 45 pounds of potash. 

 While these figures indicate the need of rather large 

 amounts of nitrogen, it is universally conceded that ex- 

 cessive applications of this element produce too much 



