10 BULLETIN 1063, U. S. DEPARTMENT OF AGRICULTURE. 



sound sweet potatoes. One decayed sweet potato left undisturbed 

 might be in contact with several sound ones, all of which would 

 eventually become diseased, but it would require considerable time 

 for all of these to decay completely. When sorted, each of the pota- 

 toes which had become infected with disease might be placed in con- 

 tact with several uninfected ones, thereby spreading the disease to 

 them. 



Since sorting increases disease injury and in addition requires 

 considerable labor, it seems inadvisable to disturb sweet potatoes 

 until they are to be placed on the market. Should decay appear 

 to be serious, the potatoes should be sorted and, if the market is at all 

 satisfactory, disposed of immediately. 



COMPARISON OF THE KEEPING QUALITIES OF VARIOUS 

 VARIETIES OF SWEET POTATOES. 



Experiments were begun in 1916 to determine the shrinkage and 

 decay in storage of the most important varieties of sweet potatoes 

 grown in the United States. These experiments were conducted in 

 the storage house at the Arlington Experimental Farm, Ya. The 

 sweet potatoes were placed in bushel crates in the field and hauled 

 to the storage house. At the house they were cleaned by wiping 

 each potato with a soft cloth. The potatoes were then placed in 

 weighed crates, and a second weighing showed the quantity stored. 

 Only one crate of a variety was used in these experiments, and with 

 some varieties there was not always a full crate. During the curing 

 period, which averaged 20 days, the temperature was maintained be- 

 tween 80° and 95° F. After this it was gradually reduced and main- 

 tained between 50° and 55° F. for the remainder of the storage 

 period. The crates of potatoes were weighed once each week during 

 the curing period and approximately once a month thereafter 

 through the storage period. One year the weights were taken every 

 day during the curing and once a week throughout the remainder of 

 the storage period. As the differences from day to day during cur- 

 ing and from week to week throughout the storage period were rather 

 slight, the figures given are based on the weights at the end of curing 

 and at monthly intervals thereafter. The results for the four years 

 1916-17 to 1919-20, inclusive, are given in Table 5. 



Table 5 shows that the average shrinkage during the curing period 

 was 7.97 per cent. The lowest shrinkage was 6.07 per cent for the 

 Big- Stem Jersey, and the highest 10.27 per cent for the Gold Skin. 

 It is worth noting that these varieties belong in the same group. 

 Excepting the Gold Skin, all the varieties in the Jersey group were 

 low to medium in shrinkage during the curing period. Of the other 

 important varieties, the shrinkage during the curing period was as 



