The Sweet Potato and its Cultivation. 229 



THE SWEET POTATO AND ITS CULTIVATION 

 ALONG THE SOUTHERN COAST BELT. 



By Chas. r. JuRiTZ, M.A., D.Sc, E.I.C., Agiicultural llesearcli 



Chemist, Capetown. 



In collection with the production of alcohol on a large scale, in order 

 to serve as a basis for liquid fuel, in view particularly of the scarcity 

 of petrol, attention has lately been turned to the possibilities of 

 utilizing' the sweet potato, which is fairly extensively cultivated along 

 the southern coast belt of the Cape Province.* At present the extent 

 of this cultivation adequately suffices to meet the demand, which is 

 restricted to the employment of the tuber as human and stock food, 

 but it is practically certain that the area indicated has potentialities 

 for sweet potato production far in excess of the demands now made 

 upon it. 



Climatic Conditions and Sweet Potato Soils. 



Sweet potatoes are best grown under climatic conditions which 

 afford sunny days and warm nights, a rainfall which is neither scanty 

 nor excessive, and which is available during a growing period of 

 from four to six months annually. Although the crop adapts itself 

 readily to other soil conditions, it attains perfection preferably in 

 light sandy loam with a more clayey, but nevertheless well-drained, 

 sub-soil. The soil must be well drained, because standing water 

 around the developing tubers is most harmful ; at the same time the 

 sub-soil should be sufhciently clayey to prevent the leaching away of 

 fertilizers and the consequent formation of long stringy tubers. 

 Fortunately for some of our southern coastal soils, which consist of 

 almost pure sand, even unpromising areas give good yields of tubers, 

 provided a reasonable supply of suitable manure be forthcoming. In 

 fact, such poor sandy soils are in some respects better suited to sweet 

 potato culture than fertile soils in which the tubers become sacrificed 

 to a profuse growth of vines or runners. If, however, sweet potatoes 

 are to be grown on poor sands, the locality should be so chosen that 

 sufficient organic matter is present in the soil, and that there is a 

 possibility of the crop obtaining such mineral plant food as suits its 

 natural tendencies. 



Mr. Robertson's Farm. 



I have drawn attention elsewhere to the fact that within the 

 Union of South Africa the Division of George and the areas adjacent 

 thereto exceed all other districts in the abundance of the sweet potato 

 crop. That statement I may now supplement by saying that no 

 planter in the Union harvests more sweet potatoes every season than 

 Mr. W. E. Robertson, whose farm is situated about three miles from 

 Little Brak River railway siding and eight miles from Mossel Bay. 



* See ar'icle on " A New Motor Spirit " by the writei', in the South African Jvurnal of 

 Industries, October, 1 920, pages 889-894. 



