130 SCIENCE IN AFRICA 



has been taken in hand and it is hoped to complete the pre- 

 liminary survey in another five years. The following soil groups 

 have been recognized and studied physically and chemically in 

 some detail: i. Laterites and lateritic red earths; 2. Yellow earths; 

 3. Grey ferruginous lateritic soils: (a) Brown to reddish-brown 

 ferruginous lateritic soils; 4. Immature mountain soils; 5. Podsolic 

 soils: (a) Prairie soils; (b) Podsolic mountain soils; 6. Subtropical 

 semi-arid soils: (a) Reddish-brown unleached soils; (b) Black 

 clays; 7. Desert soils: (a) Kalahari sand; (b) Kalahari sand on 

 lime; 8. Aeolian sandy soils; 9. Solonetz soils; 10. Solonchak soils. 

 These soil groups are climatic types, influenced, in some cases 

 markedly, by the parent material. The decisive influence of 

 climate on the course of weathering of rocks to soil in subtropical 

 conditions is clearly shown in a detailed study of a few soil types 

 in South Africa by two German scientists, Behrend and Utescher 



(1932). 



Experiments with manures in relation to the nitrogen and car- 

 bon cycles of soils have occupied much attention in South Africa. 

 Two recent papers are by Kamerman and Klintworth (1934) of 

 the division of chemistry and Williams (1932) of the Cedara 

 school of agriculture. 



Soil surveys in connection with irrigation have been developed. 

 Irrigation, especially in semi-arid regions, drastically changes the 

 chemical constitution of the soil by removing soluble material 

 from one region and depositing it elsewhere. Moreover, the irri- 

 gation of certain soils may result in widespread waterlogging. It 

 is important to foresee such results, and generally the irrigation 

 department submits proposals to the chemical division of the 

 agricultural department, which makes a detailed survey of the 

 area afiected, especially with a view to the presence of soluble 

 salts and the chemistry of the proposed water-supply. (Imperial 

 Bureau of Soil Science 1930.) 



In Southern Rhodesia there are four chemists in the department 

 of agriculture. The geological survey has also achieved pre- 

 liminary results in soil survey. Many analyses have been made, 

 but the results are not yet published. H. B. Maufe (191 5) formerly 

 director of the geological survey, has written papers on the origin 

 of Rhodesian soils from the underlying rocks. 



