340 Journal op the Department of Agriculture. 



THE SWEET POTATO AND ITS CULTIVATION 

 ALONG THE SOUTHERN COAST BELT. 



]iy CiiAS. F. JuKiTZ, M.A., D.Sc, F.I.C, Agricultuial Research 



Chemist, Capetown. 



(Tlic fii'st pjiil of lliis aiticle, now cohcIikUmI, ai)i)t'iiie(l in ]asf niontlTs 



Journal. — Editor . ) 



Chemical Composition. 



KoJViG g-ives the foUowing' as the average composition of the sweet 

 potato, according" to twelve series of analyses of tubers from dift'erent 

 countries : — 



Water 71.86 per cent. 



Protein 1.00 ,, ,, 



Fat .20 ,, ,, 



Nitrogen-free extract 25.05 ,, ,, 



Fibre 1.03 ,, ,, 



Ash .86 ,, ,, 



The above averages may be supplemented by the following figures 

 obtained by individual investigators: — 



1. 2. 3. 4. 5. 



Water 78.89 70.98 76.19 86.45 69.10 



Protein 1.28 .92 2.81 .89 1.20 



Fat 28 .49 .12^ 



(^um, etc 1.08 2.39) . ,, | ,., io 0700 



Sugar 6.86 2.69 1 '^"^^ ^"•^'^ -'"'' 



Starch 15.06 20.26 14.80. 



Fibre 98 1.20 1.T9 .49 1.32 



Ash 1.07 1.07 1.17 .55 1.32 



1. S. A¥. Johnson: Annual Report, Connecticut Agricultural Experi- 

 ment Station, U.S.A. 



2. Neubauer and Oecononiicles : Averages of three analyses of tubers 

 grown in England. 



3. Nagai and Murai : Japanese tubers. 



4 Coremvinder : Tubers from the Azores. 

 "). Coremvinder: Tubers from Malaga. 



Samples of each class of sweet potato grown by Mr. Robertson at 

 Little Brak were collected for analysis. In the laboratory each lot 

 of tubers was analysed in three parts. (1) An average sample was 

 ill each case taken of an entire tuber, including the skin. (2) Tubers 

 representing each lot were rapidly and thinly peeled and the peel 

 discarded ; a surface layer about lialf an inch in thickness was then 

 taken off for analysis all round these tubers. (3) The central core 

 remaining after removal of the above surface layer was separately 

 analysed. 



