Agriculture and Soils of the Cape Province. 



823 



Table VIII. 

 Average Composition of the three Principal Types of Witkop Soils. 



Taking- the " clieinical " Hgures first, it will be ubseivfd — 

 excepting- the fig'ure for " insoluble inorganic residue," a figure wl.'ich 

 represents that portion of the soil which is insoluble in strong a;ids, 

 and therefore of little or no use to the plant for food purposes — that 

 the figures are lowest for the sandbult type, intermediate for the 

 mixed type, and highest for the black turf group. 



Coming to the " mechanical " differences, a study of the tallies 

 will show that there are clear differences between the three typos. 

 For example, as one proceeds from the sandbult to the mixed type, 

 and thence to the black turf type, there is a marked increase in ;he 

 humus content of each group; clay likewise increases, similarly al;-o 

 the silts and the retentiveness to water. On the other hand there ai-e 

 decreases in the sand content, the sandbult type containing most and 

 the black turf least — decreases which are, as was to be expected, 

 accompanied by a diminishing permeability to water. 



In passing, it may be pointed out that (113 would fall und(>r the 

 mixed type did it contain more humus ; so also would 614 come under 

 the black turf type had it a higher humus content. 



No attempt will be made at this juncture to trace the boundaries 

 of soil types ; to do so at all accurately would necessitate much more 

 field work. Speaking approximately, the sandbult type occupies the 

 bults, the mixed turf and sand soils occupy the lower slopes of the 

 hills and mountains, while the black turf soils are found in the valley 

 bottoms, in vleis, and in kloofs. 



