SOIL SCIENCE 141 



Among recent publications on remedial measures are articles by 

 the agricultural engineer in the Rhodesia Agricultural Journal, 

 by Ducker in the Empire Cotton Growing Corporation's Journal, 

 and by Harrison in the East African Agricultural Journal. Beckley 

 (1935), the senior agricultural chemist in Kenya, has also produced 

 a valuable bulletin with many practical details of anti-erosion 

 methods which are applicable in that country. 



SOIL BIOLOGY 



The study of the flora and fauna of different soils and their 

 effects on fertility has not been highly developed, even in Europe. 

 In Africa it has scarcely been touched, though recently the divi- 

 sion of chemical services in the Union has established a small soil 

 biological section which is now studying questions relating to the 

 nitrogen cycle and humus supply in pastures and citrus orchards. 

 The study of bacteria will probably be the most fruitful on account 

 of their role in the food-cycle from soil to green plant to animal, 

 particularly in connection with the fixing of atmospheric nitrogen 

 by the roots of leguminous plants. As has been mentioned, recent 

 work, especially in Nigeria, suggests that on the whole the presence 

 of mineral salts has more influence than that of nitrogen on fertility, 

 but at the same time it is a general experience in Nigeria and else- 

 where that an intermediate crop of leguminous plants increases 

 fertility very considerably. 



Other organisms also offer wide fields for study, and may well 

 prove to be of great economic importance. The role of moulds 

 and other fungi in soil economy may rival even that of bacteria. 

 In particular, the association between fungus and plant root 

 known as Mycorrhiza is essential for the germination and growth 

 of many plants. The importance of mycorrhiza in orchids and 

 heaths is widely recognized, but it is not so v/idely known that many 

 kinds of forest trees must have the correct specific fungus in the soil 

 in order to flourish. This subject has scarcely been touched in 

 Africa, though a fair amount of work has been done on mycor- 

 rhiza in other parts of the tropics, notably by Dutch workers in the 

 East. It has been estimated that some 70 per cent, of failures to 

 re-establish plantations of local forest trees are due to lack of the 

 right mycorrhizal fungus in the soil. Again, the importance of 



