236 POTATOES 



a sweep or middle-buster, similar to that used in cotton fields. 

 Small-tooth cultivators are used on the sides of the ridges very 

 near the plants until the vines run and nearly cover the ridges. 

 When the plants are in rows only one way, in the ridge method, 

 it is necessary to use hand hoes to keep the field free from weeds. 

 The great expense of this method has caused some large growers 

 to abandon the ridge method so that horse tools can largely 

 displace the. hand hoeing. When cultivation must be stopped 

 because of the growth of the vines, the field is "laid by." In this 

 process considerable soil is moved from the middles toward the 

 rows, whether they have been in ridges or not. This will destroy 

 many of the small weeds at that time and the growth of the plants 

 will aid in keeping down future growth of weeds. 



Digging. The crop must be harvested before severe frost, 

 as the killing of .the vines by freezing may also injure the potatoes. 

 Some delay may be allowed by cutting the vines and digging the 

 roots later. If the vines are not first removed before the roots 

 are plowed out two rolling coulters on the beam of the plow are 

 used to cut the vines. A turning plow covers the vines and leaves 

 the potatoes somewhat on top of the soil. In the plowing, pick- 

 ing and handling of sweet potatoes much care must be exercised 

 to avoid bruising, as this will greatly injure their keeping qualities. 

 The potatoes are usually graded at sorting sheds or store houses, 

 rather than in the field as they are picked up. 



Storage of Sweet Potatoes. Early sweet potatoes are pro- 

 duced in southern fields for northern markets. They are 

 usually sold as soon as harvested. If they are to be kept some 

 time careful storage is necessary. Well ventilated buildings or 

 pits supplied with heat are planned for this purpose. The roots 

 should pass through a curing process, known as "sweating," at a 

 temperature of perhaps 85 or 90 degrees F. A few weeks later 

 after the curing process is completed the temperature is gradually 

 lowered to about 60 degrees, or a little less. If the ventilation is 

 good the potatoes may be held at this temperature for several 

 months. 



Diseases. Black-rot is the worst disease of the sweet potato 

 plant. It is first noticed in the shriveled condition of the terminal 

 buds of the plants. It may also be seen as small black spots on 

 the roots. After the potatoes are formed the disease appears on 

 their surface in brown patches, becoming darker at the centre of 

 each patch. The disease may first be noticed at- digging time, or 



