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 io 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 ir? 
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 
