The Sweet Potato and its Cultivation. 233 



The agricultural cliemical analyses of Mr. Eobertson's soils are 

 tabulated below: — 



No. 1. No. 2. No. 3. 



Per cent. Per cent. Per cent. 



Moisture 1.15 3.44 1.07 



Organic and volatile matter 3.37 5.34 2.64 



Nitrogen 126 .147 .070 



Potash 099 .205 .076 



Lime 144 .216 .114 



Magnesia 185 .323 .069 



Phosphoric oxide — 



Soluble in cold hydrochloric acid .041 .049 .034 



Soluble in strong boiling acids ... .081 .069 .072 



These results confirm the deduction already drawn from the 

 mechanical analyses, namely, the decided superiority of No. 2 over 

 the other two soils. It is well furnished with nitrogeneous material 

 and has a satisfactory proportion of potash, its humus-content is 

 higher than either Nos. 1 or 3, and its moisture-retaining power is 

 also better. In respect of lime it is likewise the best of the three 

 soils. No. 3, on the other hand, is chemically the poorest soil of 

 the three. It is only moderately supplied with nitrogen, potash, and 

 lime, and its proportion of humus and capacity for retaining water 

 are comparatively low. Its available supply of phosphate is also 

 scantier than in the other two soils, although it must be said that in 

 respect of phosphate there is not much to choose between the three ; 

 all alike have no more than a " fair " reserve of phosphoric oxide. 



Varieties of Sweet Potato. 



Four varieties of sweet potato were being grown on the farm at 

 Little Brak River on the occasion of my visit: — 



1. Common six-months. 



2. Red-skinned three-mouths. 



3. Yellow-skinned three-months. 



4. British East African white-skinned. 



The six-months variety is the kind for which the demand is 

 greatest all over the Union, on account of its keeping qualities. This 

 variety, moreover, is said to stand transport and rough treatment 

 better, and, under adverse circumstances, to give a larger yield per 

 acre, than any of the other kinds. The tuber, however, is stated to 

 be more fibrous than in any other variety. The midribs and veins 

 on the underside of the leaves of this class of sweet potato are purple. 



The red-skinned type is the most delicate potato of the four, and 

 the demand for it is only one-ninetieth of that for the six-months 

 variety. Its tubers require the greatest care in handling, and the 

 cultivation of the plant itself gives more difficulty than the other 

 varieties do. This variety has the leaf-ribs wholly green on both 

 s^'des- 



The yellow three-months tuber also needs special cultural care, 

 but not to the same degree as the red-skinned. Both these quick- 

 growing three-months varieties, however, are said to be more watery 



