The Sweet Potato and its Cultivation. 349 



very suitable for soils deficient in humus, a type which prevails along 

 our own southern coast belt. 



The sweet potato, too, is already in use in other countries tor the 

 production of alcohol, and is stated to be so used in the Azores and 

 West Indies* as well as in Brazil and Algiers. It is more easily 

 raised, makes a larger yield per acre, is probably a heavier and 

 cheaper starch producer, in regions where it can be cultivated, than 

 even the common potato, and should serve excellently as a raw 

 material for the production of industrial alcohol. The common potato 

 (Solanum tuberosum, L.), containing about 75 per cent, of water, 

 yields from 16 to 24 per cent, of starch, and in Germany 100 kg. 

 of potatoes, containing 20 per cent, of starch, are reckoned to yield 

 in practice from II3 to 12 litres of absolute alcohol. The sweet 

 potato (Ipomora batatas, Linn.), with an average water content, 

 according to Konig's compilations, of about 72 per cent., contains 

 approximately 25 per cent, of starch and sugar, from 2 to 3| per cent, 

 whereof consists of sugar. A yield of sweet potato tubers of this 

 composition at the rate of 8 tons of 2000 lb. per morgen (say, 4 tons 

 per acre) should produce over 1000 litres (220 gallons) of absolute 

 alcohol per morgen. 



InvestictATIons in the United States. 



A few years ago systematic investigations were begun under the 

 ac ministration of the United States Department of Agriculture for 

 the purpose of determining the identity of different varieties of sweet 

 potatoes and for developing the most suitable method of utilizing the 

 plant as a stock food in regions where it can be cheaply produced. 

 Efforts were also made to solve the problems and cultural difficulties 

 of sweet potato growers. A general investigation was carried on at 

 the same time of dry rot, stem rot, and other diseases of the sweet 

 potato, and the remedial measures were studied and suitable treat- 

 ment recommended. 



The sweet potato tubers, after unearthing, are said to become 

 sweeter on exposure to the sun's rays; tubers which have been so 

 exposed are also believed to keep longer than others. Mr. Robertson 

 informs me, ho-wever, that if unearthing is carried out later than 

 October the tubers may be scorched by the sun's heat in a single 

 day. On the other hand, exposure to frost is alleged to spoil un- 

 earthed tubers; the runners are easily injured by light frosts which 

 do not appreciably affect the tubers, but if the runners become 

 actually frozen the tubers are liable to injury from the frozen sap 

 passing down into them, and this may cause speedy decay after as 

 well as before harvesting. Hence when the runners have been killed by 

 frost immediate action should be taken ; either the sweet potatoes 

 should be dug up, or else the runners should be cut away from the 

 tubers and an additional protecting layer of soil thrown over the 

 latter. 



In jSforth America there is a good deal of sweet potato culture 

 carried on in the Eastern States, Florida, Georgia, South Carolina, 



* ]'lde Siinni(ii,ds, op. cit., pp. 22, 23. Mr. B. H. Cousins, DirLClor of Agriculture, 

 Jamaica, however, informs nie that, as far as he is aware, no alcoholihasever been made com- 

 mercially in the West Indies, and certainly not in Jamaica, from sweet potatoes. At the 

 present time, he says, the tul)ers are selling at alxmt t'20 jier ton, with a gravely inadequate 

 supply for the food requirements of the country. 



