14 CHAPTER II 



warmth, while the second rises in temperature as it approaches 

 the equator. 



Altitude is also of importance in this connection. The 

 growing season is naturally shorter and the nights often cooler 

 on the inland plateaux than at low altitudes. Thus we find 

 that cowpeas in high altitudes will be found more useful than 

 velvet beans; flint maize better than dent maize, and so on. 



Latitude naturally also affects the length of growing 

 season, but its effect is not so apparent in the Union, because 

 this is largely offset by the increase in altitude from south to 

 north. 



Soils of South Africa. — As must be expected from the 

 widely differing geographical formations, the soils from these 

 are very divergent in character and productivity. For example, 

 those derived from the Bokkeveld series, composed of soft sand- 

 stones and shales, are very fertile soils and markedly different 

 from the poor sandy soils formed from the often adjacent Table 

 Mountain sandstone series, composed of highly siliceous rocks 

 which weather into coarse, angular fragments. 



In general it may be said that the soils of the sub-continent 

 are markedly deficient in phosphates, but moderately well sup- 

 plied with potash and nitrogen. That they usually contain 

 sufficient nitrogen is fortunate, as the application of artificial 

 nitrogenous fertilisers is an expensive item in countries not 

 favourably situated in regard to supply. 



It is impossible to deal with the subject of South African 

 soils in detail. However, certain areas have predominating 

 types, and these are briefly given : — 



(1) The South- West Cape. — The soils of this region are 

 on the whole poor in fertility, of a light, sandy texture, and of 

 low humus content. Loams do occur, but unfortunately the 

 physical condition of these has deteriorated owing to the poor 

 methods of farming practised. 



(2) South and South-Eastern Coastal Belt. — Fine sandy 

 loams prevail here ; the nitrogen content is usually higher than 

 in those of the south-west Cape, and more lime is found, but 

 phosphates remain low. 



(3) Namaqualancl. — Chiefly sandy soils, poor in humus 

 and nitrogen, occur. In some cases calcareous soils are found, 

 and a clay soil found in the Calvinia area appears to be well 

 supplied with phosphates. 



