20 BULLETIN 50, HAWAII EXPERIMENT STATION. 
In a test made to determine the effect of pruning on yield, it was 
found that production was considerably decreased when the vines 
were cut back. Apparently the shorter the vine is cut, the greater 
will be the reduction in yield of roots. Yield is largely influenced 
by the locality and the soil where the crop is grown, the kind and 
amount of fertilizer used, the cultivation given, and finally by the 
variety itself. It may be increased by proper cultivation and the 
application of fertilizers, or by the selection through several genera- 
tions of individual hills producing heavy crops of well-shaped roots. 
The period of harvesting differs with the different varieties. Yel- 
lowing of the leaves is not always an indication of ripening and may 
be due to the disease known as stem-end rot. 
Unfortunately the sweet potato is not graded in Hawaii. Stand- 
ardization will hardly become a reality until uniformity of size, 
shape, and color is taken into consideration, and the roots are mar- 
keted free from defects resulting from careless handling, diseases, 
and insect pests. Regular-shaped, uniform, smooth, firm, and 
fresh-looking potatoes should be selected for home use. 
The problem of storage can be eliminated by harvesting just 
enough potatoes to meet the needs of the wholesaler or the house- 
holder. When they are to be held for some time, sweet potatoes 
should be carefully stored to reduce to a minimum the loss by 
shrinkage. 
The sweet-potato plant is attacked by a number of insect pests 
and fungus diseases which can be brought under control by the use 
of proper measures. 
In chemical composition the sweet potato compares very favor- 
ably with taro, cassava, and potato. 
On account of their high feeding value, sweet-potato vines should 
be used as feed for farm animals. They are greatly relished by hogs 
and dairy cattle, and when it is desired to practice economy of labor 
in harvesting, the former may be turned in to harvest the roots, 
after the latter have been allowed to pasture the vines. 
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